Arduino Music: Notes and Chord Detector

This project presents program to detect musical notes and chords using Arduino (nano or above).

Jul 12, 2020

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chord

notes

music

Components and supplies

Arduino Nano R3

Max4466

Apps and platforms

Arduino IDE

Project description

Code

Note detection program

arduino

This program will print the detected note name. Refer the comment within code for clarification.

1//---------------------------------------------------------------------------//
2int   in[128];
3byte NoteV[13]={8,23,40,57,76,96,116,138,162,187,213,241,255}; //data   for note detection based on frequency
4float f_peaks[5]; // top 5 frequencies   peaks in descending order
5int Mic_pin;  
6//---------------------------------------------------------------------------//
7
8
9void   setup() {
10Serial.begin(250000);
11Mic_pin = A7;   // change as per Microphone   pin
12}
13
14
15void loop() 
16{
17  Tone_det();
18
19}
20
21
22//-----------------------------Tone   Detection Function----------------------------------------------//
23// Documentation   on Tone_detection:https://www.instructables.com/member/abhilash_patel/instructables/
24//   Code Written By: Abhilash Patel
25// Contact: abhilashpatel121@gmail.com
26//   This code written for arduino Nano board (should also work for UNO)
27// This code   won't work for any board having RAM less than 2kb,
28
29
30
31void Tone_det()
32{   long unsigned int a1,b,a2;
33  float a;
34  float sum1=0,sum2=0;
35  float sampling;
36   a1=micros();
37        for(int i=0;i<128;i++)
38          {
39            a=analogRead(Mic_pin)-500;      //rough zero shift
40            //utilising time between two sample for windowing   & amplitude calculation
41            sum1=sum1+a;              //to average value
42             sum2=sum2+a*a;            // to RMS value
43            a=a*(sin(i*3.14/128)*sin(i*3.14/128));    // Hann window
44            in[i]=10*a;                // scaling for float   to int conversion
45            delayMicroseconds(195);   // based on operation   frequency range
46          }
47b=micros();
48
49sum1=sum1/128;               //   Average amplitude
50sum2=sqrt(sum2/128);         // RMS
51sampling= 128000000/(b-a1);   // real time sampling frequency
52
53//for very low or no amplitude, this code   wont start
54//it takes very small aplitude of sound to initiate for value sum2-sum1>3,   
55//change sum2-sum1 threshold based on requirement
56if(sum2-sum1>3){  
57        FFT(128,sampling);        
58       //EasyFFT based optimised  FFT code,   
59       //this code updates f_peaks array with 5 most dominent frequency in descending   order
60 
61 for(int i=0;i<12;i++){in[i]=0;}  // utilising in[] array for further   calculation
62
63int j=0,k=0; //below loop will convert frequency value to note   
64       for(int i=0; i<5;i++)
65           {
66           if(f_peaks[i]>1040){f_peaks[i]=0;}
67            if(f_peaks[i]>=65.4   && f_peaks[i]<=130.8) {f_peaks[i]=255*((f_peaks[i]/65.4)-1);}
68            if(f_peaks[i]>=130.8  && f_peaks[i]<=261.6) {f_peaks[i]=255*((f_peaks[i]/130.8)-1);}
69            if(f_peaks[i]>=261.6  && f_peaks[i]<=523.25){f_peaks[i]=255*((f_peaks[i]/261.6)-1);}
70            if(f_peaks[i]>=523.25 && f_peaks[i]<=1046)  {f_peaks[i]=255*((f_peaks[i]/523.25)-1);}
71            if(f_peaks[i]>=1046 && f_peaks[i]<=2093)  {f_peaks[i]=255*((f_peaks[i]/1046)-1);}
72            if(f_peaks[i]>255){f_peaks[i]=254;}
73           j=1;k=0;
74         
75          while(j==1)
76              {
77              if(f_peaks[i]<NoteV[k]){f_peaks[i]=k;j=0;}
78               k++;  // a note with max peaks (harmonic) with aplitude priority is   selected
79              if(k>15){j=0;}
80              }
81
82              if(f_peaks[i]==12){f_peaks[i]=0;}
83               k=f_peaks[i];
84              in[k]=in[k]+(5-i);
85            }
86
87k=0;j=0;
88           for(int i=0;i<12;i++)
89             {
90              if(k<in[i]){k=in[i];j=i;}   //Max value detection
91             }
92       // Note print
93       // if   you need to use note value for some application, use of note number recomendded
94        // where, 0=c;1=c#,2=D;3=D#;.. 11=B;      
95       //a2=micros(); // time   check
96        k=j;
97        if(k==0) {Serial.println('C');}
98        if(k==1)   {Serial.print('C');Serial.println('#');}
99        if(k==2) {Serial.println('D');}
100         if(k==3) {Serial.print('D');Serial.println('#');}
101        if(k==4) {Serial.println('E');}
102         if(k==5) {Serial.println('F');}
103        if(k==6) {Serial.print('F');Serial.println('#');}
104         if(k==7) {Serial.println('G');}
105        if(k==8) {Serial.print('G');Serial.println('#');}
106         if(k==9) {Serial.println('A');}
107        if(k==10){Serial.print('A');Serial.println('#');}
108         if(k==11){Serial.println('B');}
109       }
110}
111
112//-----------------------------FFT   Function----------------------------------------------//
113// Documentation on   EasyFFT:https://www.instructables.com/member/abhilash_patel/instructables/
114//   EasyFFT code optimised for 128 sample size to reduce mamory consumtion
115
116float   FFT(byte N,float Frequency)
117{
118byte data[8]={1,2,4,8,16,32,64,128};
119int   a,c1,f,o,x;
120a=N;  
121                                 
122      for(int i=0;i<8;i++)                  //calculating the levels
123         { if(data[i]<=a){o=i;} }
124       o=7;
125byte in_ps[data[o]]={};     //input for sequencing
126float out_r[data[o]]={};    //real part of transform
127float out_im[data[o]]={};  //imaginory part of transform
128            
129x=0;  
130      for(int b=0;b<o;b++)                     // bit reversal
131          {
132          c1=data[b];
133          f=data[o]/(c1+c1);
134                for(int   j=0;j<c1;j++)
135                    { 
136                     x=x+1;
137                     in_ps[x]=in_ps[j]+f;
138                     }
139         }
140 
141      for(int i=0;i<data[o];i++)            //   update input array as per bit reverse order
142         {
143          if(in_ps[i]<a)
144           {out_r[i]=in[in_ps[i]];}
145          if(in_ps[i]>a)
146          {out_r[i]=in[in_ps[i]-a];}       
147         }
148
149int i10,i11,n1;
150float e,c,s,tr,ti;
151
152    for(int   i=0;i<o;i++)                                    //fft
153    {
154     i10=data[i];               // overall values of sine cosine  
155     i11=data[o]/data[i+1];     // loop with similar sine cosine
156     e=6.283/data[i+1];
157     e=0-e;
158      n1=0;
159
160          for(int j=0;j<i10;j++)
161          {
162          c=cos(e*j);   
163          s=sin(e*j); 
164          n1=j;
165          
166                for(int   k=0;k<i11;k++)
167                 {
168                 tr=c*out_r[i10+n1]-s*out_im[i10+n1];
169                  ti=s*out_r[i10+n1]+c*out_im[i10+n1];
170          
171                 out_r[n1+i10]=out_r[n1]-tr;
172                  out_r[n1]=out_r[n1]+tr;
173          
174                 out_im[n1+i10]=out_im[n1]-ti;
175                  out_im[n1]=out_im[n1]+ti;          
176          
177                 n1=n1+i10+i10;
178                   }       
179             }
180     }
181
182//---> here onward   out_r contains amplitude and our_in conntains frequency (Hz)
183    for(int i=0;i<data[o-1];i++)                // getting amplitude from compex number
184        {
185         out_r[i]=sqrt((out_r[i]*out_r[i])+(out_im[i]*out_im[i]));   // to  increase the speed delete sqrt
186         out_im[i]=(i*Frequency)/data[o];
187          /*
188         Serial.print(out_im[i],2); Serial.print("Hz");
189         Serial.print("\	");                             // uncomment to print freuency bin    
190         Serial.println(out_r[i]);   
191         */
192        }
193
194x=0;       // peak detection
195   for(int i=1;i<data[o-1]-1;i++)
196       {
197      if(out_r[i]>out_r[i-1] && out_r[i]>out_r[i+1]) 
198      {in_ps[x]=i;     //in_ps array used for storage of peak number
199      x=x+1;}    
200      }
201
202s=0;
203c=0;
204     for(int i=0;i<x;i++)             // re arraange as per magnitude
205    {
206         for(int j=c;j<x;j++)
207        {
208            if(out_r[in_ps[i]]<out_r[in_ps[j]])   
209                {s=in_ps[i];
210                in_ps[i]=in_ps[j];
211                in_ps[j]=s;}
212         }
213    c=c+1;
214    }
215    
216    for(int i=0;i<5;i++)     // updating   f_peak array (global variable)with descending order
217     {
218     f_peaks[i]=(out_im[in_ps[i]-1]*out_r[in_ps[i]-1]+out_im[in_ps[i]]*out_r[in_ps[i]]+out_im[in_ps[i]+1]*out_r[in_ps[i]+1])
219      /(out_r[in_ps[i]-1]+out_r[in_ps[i]]+out_r[in_ps[i]+1]);
220     }
221}
222     
223//------------------------------------------------------------------------------------//

//---------------------------------------------------------------------------//
int   in[128];
byte NoteV[13]={8,23,40,57,76,96,116,138,162,187,213,241,255}; //data   for note detection based on frequency
float f_peaks[5]; // top 5 frequencies   peaks in descending order
int Mic_pin;  
//---------------------------------------------------------------------------//


void   setup() {
Serial.begin(250000);
Mic_pin = A7;   // change as per Microphone   pin
}


void loop() 
{
  Tone_det();

}


//-----------------------------Tone   Detection Function----------------------------------------------//
// Documentation   on Tone_detection:https://www.instructables.com/member/abhilash_patel/instructables/
//   Code Written By: Abhilash Patel
// Contact: abhilashpatel121@gmail.com
//   This code written for arduino Nano board (should also work for UNO)
// This code   won't work for any board having RAM less than 2kb,



void Tone_det()
{   long unsigned int a1,b,a2;
  float a;
  float sum1=0,sum2=0;
  float sampling;
   a1=micros();
        for(int i=0;i<128;i++)
          {
            a=analogRead(Mic_pin)-500;      //rough zero shift
            //utilising time between two sample for windowing   & amplitude calculation
            sum1=sum1+a;              //to average value
             sum2=sum2+a*a;            // to RMS value
            a=a*(sin(i*3.14/128)*sin(i*3.14/128));    // Hann window
            in[i]=10*a;                // scaling for float   to int conversion
            delayMicroseconds(195);   // based on operation   frequency range
          }
b=micros();

sum1=sum1/128;               //   Average amplitude
sum2=sqrt(sum2/128);         // RMS
sampling= 128000000/(b-a1);   // real time sampling frequency

//for very low or no amplitude, this code   wont start
//it takes very small aplitude of sound to initiate for value sum2-sum1>3,   
//change sum2-sum1 threshold based on requirement
if(sum2-sum1>3){  
        FFT(128,sampling);        
       //EasyFFT based optimised  FFT code,   
       //this code updates f_peaks array with 5 most dominent frequency in descending   order
 
 for(int i=0;i<12;i++){in[i]=0;}  // utilising in[] array for further   calculation

int j=0,k=0; //below loop will convert frequency value to note   
       for(int i=0; i<5;i++)
           {
           if(f_peaks[i]>1040){f_peaks[i]=0;}
            if(f_peaks[i]>=65.4   && f_peaks[i]<=130.8) {f_peaks[i]=255*((f_peaks[i]/65.4)-1);}
            if(f_peaks[i]>=130.8  && f_peaks[i]<=261.6) {f_peaks[i]=255*((f_peaks[i]/130.8)-1);}
            if(f_peaks[i]>=261.6  && f_peaks[i]<=523.25){f_peaks[i]=255*((f_peaks[i]/261.6)-1);}
            if(f_peaks[i]>=523.25 && f_peaks[i]<=1046)  {f_peaks[i]=255*((f_peaks[i]/523.25)-1);}
            if(f_peaks[i]>=1046 && f_peaks[i]<=2093)  {f_peaks[i]=255*((f_peaks[i]/1046)-1);}
            if(f_peaks[i]>255){f_peaks[i]=254;}
           j=1;k=0;
         
          while(j==1)
              {
              if(f_peaks[i]<NoteV[k]){f_peaks[i]=k;j=0;}
               k++;  // a note with max peaks (harmonic) with aplitude priority is   selected
              if(k>15){j=0;}
              }

              if(f_peaks[i]==12){f_peaks[i]=0;}
               k=f_peaks[i];
              in[k]=in[k]+(5-i);
            }

k=0;j=0;
           for(int i=0;i<12;i++)
             {
              if(k<in[i]){k=in[i];j=i;}   //Max value detection
             }
       // Note print
       // if   you need to use note value for some application, use of note number recomendded
        // where, 0=c;1=c#,2=D;3=D#;.. 11=B;      
       //a2=micros(); // time   check
        k=j;
        if(k==0) {Serial.println('C');}
        if(k==1)   {Serial.print('C');Serial.println('#');}
        if(k==2) {Serial.println('D');}
         if(k==3) {Serial.print('D');Serial.println('#');}
        if(k==4) {Serial.println('E');}
         if(k==5) {Serial.println('F');}
        if(k==6) {Serial.print('F');Serial.println('#');}
         if(k==7) {Serial.println('G');}
        if(k==8) {Serial.print('G');Serial.println('#');}
         if(k==9) {Serial.println('A');}
        if(k==10){Serial.print('A');Serial.println('#');}
         if(k==11){Serial.println('B');}
       }
}

//-----------------------------FFT   Function----------------------------------------------//
// Documentation on   EasyFFT:https://www.instructables.com/member/abhilash_patel/instructables/
//   EasyFFT code optimised for 128 sample size to reduce mamory consumtion

float   FFT(byte N,float Frequency)
{
byte data[8]={1,2,4,8,16,32,64,128};
int   a,c1,f,o,x;
a=N;  
                                 
      for(int i=0;i<8;i++)                  //calculating the levels
         { if(data[i]<=a){o=i;} }
       o=7;
byte in_ps[data[o]]={};     //input for sequencing
float out_r[data[o]]={};    //real part of transform
float out_im[data[o]]={};  //imaginory part of transform
            
x=0;  
      for(int b=0;b<o;b++)                     // bit reversal
          {
          c1=data[b];
          f=data[o]/(c1+c1);
                for(int   j=0;j<c1;j++)
                    { 
                     x=x+1;
                     in_ps[x]=in_ps[j]+f;
                     }
         }
 
      for(int i=0;i<data[o];i++)            //   update input array as per bit reverse order
         {
          if(in_ps[i]<a)
           {out_r[i]=in[in_ps[i]];}
          if(in_ps[i]>a)
          {out_r[i]=in[in_ps[i]-a];}       
         }

int i10,i11,n1;
float e,c,s,tr,ti;

    for(int   i=0;i<o;i++)                                    //fft
    {
     i10=data[i];               // overall values of sine cosine  
     i11=data[o]/data[i+1];     // loop with similar sine cosine
     e=6.283/data[i+1];
     e=0-e;
      n1=0;

          for(int j=0;j<i10;j++)
          {
          c=cos(e*j);   
          s=sin(e*j); 
          n1=j;
          
                for(int   k=0;k<i11;k++)
                 {
                 tr=c*out_r[i10+n1]-s*out_im[i10+n1];
                  ti=s*out_r[i10+n1]+c*out_im[i10+n1];
          
                 out_r[n1+i10]=out_r[n1]-tr;
                  out_r[n1]=out_r[n1]+tr;
          
                 out_im[n1+i10]=out_im[n1]-ti;
                  out_im[n1]=out_im[n1]+ti;          
          
                 n1=n1+i10+i10;
                   }       
             }
     }

//---> here onward   out_r contains amplitude and our_in conntains frequency (Hz)
    for(int i=0;i<data[o-1];i++)                // getting amplitude from compex number
        {
         out_r[i]=sqrt((out_r[i]*out_r[i])+(out_im[i]*out_im[i]));   // to  increase the speed delete sqrt
         out_im[i]=(i*Frequency)/data[o];
          /*
         Serial.print(out_im[i],2); Serial.print("Hz");
         Serial.print("\	");                             // uncomment to print freuency bin    
         Serial.println(out_r[i]);   
         */
        }

x=0;       // peak detection
   for(int i=1;i<data[o-1]-1;i++)
       {
      if(out_r[i]>out_r[i-1] && out_r[i]>out_r[i+1]) 
      {in_ps[x]=i;     //in_ps array used for storage of peak number
      x=x+1;}    
      }

s=0;
c=0;
     for(int i=0;i<x;i++)             // re arraange as per magnitude
    {
         for(int j=c;j<x;j++)
        {
            if(out_r[in_ps[i]]<out_r[in_ps[j]])   
                {s=in_ps[i];
                in_ps[i]=in_ps[j];
                in_ps[j]=s;}
         }
    c=c+1;
    }
    
    for(int i=0;i<5;i++)     // updating   f_peak array (global variable)with descending order
     {
     f_peaks[i]=(out_im[in_ps[i]-1]*out_r[in_ps[i]-1]+out_im[in_ps[i]]*out_r[in_ps[i]]+out_im[in_ps[i]+1]*out_r[in_ps[i]+1])
      /(out_r[in_ps[i]-1]+out_r[in_ps[i]]+out_r[in_ps[i]+1]);
     }
}
     
//------------------------------------------------------------------------------------//

Chord detection program

arduino

1//---------------------------------------------------------------------------//
2int   in[128];
3byte NoteV[13]={8,23,40,57,76,96,116,138,162,187,213,241,255};
4float   f_peaks[8]; // top 8 frequencies peaks in descending order
5//---------------------------------------------------------------------------//
6
7
8void   setup() {
9Serial.begin(250000);
10}
11
12
13void loop() 
14{ 
15  Chord_det();
16
17}
18
19
20//-----------------------------Chord   Detection Function----------------------------------------------//
21// Documentation   on Chord_detection:https://www.instructables.com/member/abhilash_patel/instructables/
22//   Code Written By: Abhilash Patel
23// Contact: abhilashpatel121@gmail.com
24//   this code written for arduino Nano board (should also  work for UNO) or better board
25//   this code won't work for any board having RAM less than 2kb,
26// More accurate   detection can be carried out on more powerful borad by increasing sample size
27
28
29
30void   Chord_det()
31{ 
32  long unsigned int a1,b,a2;
33  float a;
34  float sum1=0,sum2=0;
35   float sampling;
36  a1=micros();
37        for(int i=0;i<128;i++)
38          {
39             a=analogRead(A7)-500;     //rough zero shift
40            //utilising   time between two sample for windowing & amplitude calculation
41            sum1=sum1+a;               //to average value
42            sum2=sum2+a*a;            // to   RMS value
43            a=a*(sin(i*3.14/128)*sin(i*3.14/128));   // Hann window
44             in[i]=4*a;                // scaling for float to int conversion
45             delayMicroseconds(195);   // based on operation frequency range
46           }
47b=micros(); 
48sum1=sum1/128;               //average amplitude
49sum2=sqrt(sum2/128);          //RMS amplitude
50sampling= 128000000/(b-a1);  // real time sampling frequency
51
52//for   very low or no amplitude, this code wont start
53//it takes very small aplitude   of sound to initiate for value sum2-sum1>3, 
54//change sum2-sum1 threshold based   on requirement
55if(sum2-sum1>3){   
56       FFT(128,sampling);        //EasyFFT   based optimised  FFT code
57        
58             
59              for(int   i=0;i<12;i++){in[i]=0;}
60
61int j=0,k=0; //below loop will convert frequency   value to note 
62       for(int i=0; i<8;i++)
63           {
64           if(f_peaks[i]>1040){f_peaks[i]=0;}
65            if(f_peaks[i]>=65.4   && f_peaks[i]<=130.8) {f_peaks[i]=255*((f_peaks[i]/65.4)-1);}
66            if(f_peaks[i]>=130.8  && f_peaks[i]<=261.6) {f_peaks[i]=255*((f_peaks[i]/130.8)-1);}
67            if(f_peaks[i]>=261.6  && f_peaks[i]<=523.25){f_peaks[i]=255*((f_peaks[i]/261.6)-1);}
68            if(f_peaks[i]>=523.25 && f_peaks[i]<=1046)  {f_peaks[i]=255*((f_peaks[i]/523.25)-1);}
69            if(f_peaks[i]>=1046 && f_peaks[i]<=2093)  {f_peaks[i]=255*((f_peaks[i]/1046)-1);}
70            if(f_peaks[i]>255){f_peaks[i]=254;}
71           j=1;k=0;
72         while(j==1)
73               {
74              if(f_peaks[i]<=NoteV[k]){f_peaks[i]=k;j=0;}
75               k++;  // a note with max peaks (harmonic) with aplitude priority is   selected
76              if(k>15){j=0;}
77              }
78
79              if(f_peaks[i]==12){f_peaks[i]=0;}
80               k=f_peaks[i];
81              in[k]=in[k]+(8-i);
82             }
83
84k=0;j=0;
85           for(int i=0;i<12;i++)
86             {
87              if(k<in[i]){k=in[i];j=i;}   //Max value detection
88             }
89
90          for(int i=0;i<8;i++)
91              {
92              in[12+i]=in[i];
93             }        
94
95for   (int i=0;i<12;i++)
96{
97  in[20+i]=in[i]*in[i+4]*in[i+7];
98  in[32+i]=in[i]*in[i+3]*in[i+7];    //all chord check
99}
100
101
102for (int i=0;i<24;i++)
103{
104in[i]=in[i+20];
105if(k<in[i]){k=in[i];j=i;}    // picking chord with max possiblity
106}
107char chord_out;
108int chord=j;
109if(chord>11){chord=chord-12;chord_out='m';}   //Mojor-minor check
110else{chord_out=' ';}
111
112// Here "chord" variable has   value of detected chord,
113// 0-11 defines all majot chord from C,C#,D,D#,.. B
114//12-23   defines all minor chord from Cm,C#m,Dm,D#m,.. Bm
115
116  
117   a2=micros();
118         k=chord;
119        if(k==0){Serial.print('C');Serial.println(chord_out);}
120         if(k==1){Serial.print('C');Serial.print('#');Serial.println(chord_out);}
121         if(k==2){Serial.print('D');Serial.println(chord_out);}
122        if(k==3){Serial.print('D');Serial.print('#');Serial.println(chord_out);}
123         if(k==4){Serial.print('E');Serial.println(chord_out);}
124        if(k==5){Serial.print('F');Serial.println(chord_out);}
125         if(k==6){Serial.print('F');Serial.print('#');Serial.println(chord_out);}
126         if(k==7){Serial.print('G');Serial.println(chord_out);}
127        if(k==8){Serial.print('G');Serial.print('#');Serial.println(chord_out);}
128         if(k==9){Serial.print('A');Serial.println(chord_out);}
129        if(k==10){Serial.print('A');Serial.print('#');Serial.println(chord_out);}
130         if(k==11){Serial.print('B');Serial.println(chord_out);}
131       }
132        
133}
134
135//-----------------------------FFT Function----------------------------------------------//
136//   Documentation on EasyFFT:https://www.instructables.com/member/abhilash_patel/instructables/
137//   EasyFFT code optimised for 128 sample size to reduce mamory consumtion
138
139float   FFT(byte N,float Frequency)
140{
141byte data[8]={1,2,4,8,16,32,64,128};
142int   a,c1,f,o,x;
143a=N;  
144                                 
145      for(int i=0;i<8;i++)                  //calculating the levels
146         { if(data[i]<=a){o=i;} }
147       o=7;
148byte in_ps[data[o]]={};     //input for sequencing
149float out_r[data[o]]={};    //real part of transform
150float out_im[data[o]]={};  //imaginory part of transform
151            
152x=0;  
153      for(int b=0;b<o;b++)                     // bit reversal
154          {
155          c1=data[b];
156          f=data[o]/(c1+c1);
157                for(int   j=0;j<c1;j++)
158                    { 
159                     x=x+1;
160                     in_ps[x]=in_ps[j]+f;
161                     }
162         }
163 
164      for(int i=0;i<data[o];i++)            //   update input array as per bit reverse order
165         {
166          if(in_ps[i]<a)
167           {out_r[i]=in[in_ps[i]];}
168          if(in_ps[i]>a)
169          {out_r[i]=in[in_ps[i]-a];}       
170         }
171
172
173int i10,i11,n1;
174float e,c,s,tr,ti;
175
176    for(int   i=0;i<o;i++)                                    //fft
177    {
178     i10=data[i];               // overall values of sine cosine  
179     i11=data[o]/data[i+1];     // loop with similar sine cosine
180     e=6.283/data[i+1];
181     e=0-e;
182      n1=0;
183
184          for(int j=0;j<i10;j++)
185          {
186          c=cos(e*j);   
187          s=sin(e*j); 
188          n1=j;
189          
190                for(int   k=0;k<i11;k++)
191                 {
192                 tr=c*out_r[i10+n1]-s*out_im[i10+n1];
193                  ti=s*out_r[i10+n1]+c*out_im[i10+n1];
194          
195                 out_r[n1+i10]=out_r[n1]-tr;
196                  out_r[n1]=out_r[n1]+tr;
197          
198                 out_im[n1+i10]=out_im[n1]-ti;
199                  out_im[n1]=out_im[n1]+ti;          
200          
201                 n1=n1+i10+i10;
202                   }       
203             }
204     }
205
206/*
207for(int i=0;i<data[o];i++)
208{
209Serial.print(out_r[i]);
210Serial.print("\	");                                      // uncomment to print RAW o/p    
211Serial.print(out_im[i]);   Serial.println("i");      
212}
213*/
214
215//---> here onward out_r contains   amplitude and our_in conntains frequency (Hz)
216    for(int i=0;i<data[o-1];i++)                // getting amplitude from compex number
217        {
218         out_r[i]=sqrt((out_r[i]*out_r[i])+(out_im[i]*out_im[i]));   // to  increase the speed delete sqrt
219         out_im[i]=(i*Frequency)/data[o];
220          /*
221         Serial.print(out_im[i],2); Serial.print("Hz");
222         Serial.print("\	");                             // uncomment to print freuency bin    
223         Serial.println(out_r[i]);   
224         */
225        }
226
227x=0;       // peak detection
228   for(int i=1;i<data[o-1]-1;i++)
229       {
230      if(out_r[i]>out_r[i-1] && out_r[i]>out_r[i+1]) 
231      {in_ps[x]=i;     //in_ps array used for storage of peak number
232      x=x+1;}    
233      }
234
235s=0;
236c=0;
237     for(int i=0;i<x;i++)             // re arraange as per magnitude
238    {
239         for(int j=c;j<x;j++)
240        {
241            if(out_r[in_ps[i]]<out_r[in_ps[j]])   
242                {s=in_ps[i];
243                in_ps[i]=in_ps[j];
244                in_ps[j]=s;}
245         }
246    c=c+1;
247    }
248    
249    for(int i=0;i<8;i++)     // updating   f_peak array (global variable)with descending order
250    {
251     // f_peaks[i]=out_im[in_ps[i]];Serial.println(f_peaks[i]);
252      f_peaks[i]=(out_im[in_ps[i]-1]*out_r[in_ps[i]-1]+out_im[in_ps[i]]*out_r[in_ps[i]]+out_im[in_ps[i]+1]*out_r[in_ps[i]+1])
253      /(out_r[in_ps[i]-1]+out_r[in_ps[i]]+out_r[in_ps[i]+1]);
254     // Serial.println(f_peaks[i]);
255     } 
256}
257    
258//------------------------------------------------------------------------------------//

//---------------------------------------------------------------------------//
int   in[128];
byte NoteV[13]={8,23,40,57,76,96,116,138,162,187,213,241,255};
float   f_peaks[8]; // top 8 frequencies peaks in descending order
//---------------------------------------------------------------------------//


void   setup() {
Serial.begin(250000);
}


void loop() 
{ 
  Chord_det();

}


//-----------------------------Chord   Detection Function----------------------------------------------//
// Documentation   on Chord_detection:https://www.instructables.com/member/abhilash_patel/instructables/
//   Code Written By: Abhilash Patel
// Contact: abhilashpatel121@gmail.com
//   this code written for arduino Nano board (should also  work for UNO) or better board
//   this code won't work for any board having RAM less than 2kb,
// More accurate   detection can be carried out on more powerful borad by increasing sample size



void   Chord_det()
{ 
  long unsigned int a1,b,a2;
  float a;
  float sum1=0,sum2=0;
   float sampling;
  a1=micros();
        for(int i=0;i<128;i++)
          {
             a=analogRead(A7)-500;     //rough zero shift
            //utilising   time between two sample for windowing & amplitude calculation
            sum1=sum1+a;               //to average value
            sum2=sum2+a*a;            // to   RMS value
            a=a*(sin(i*3.14/128)*sin(i*3.14/128));   // Hann window
             in[i]=4*a;                // scaling for float to int conversion
             delayMicroseconds(195);   // based on operation frequency range
           }
b=micros(); 
sum1=sum1/128;               //average amplitude
sum2=sqrt(sum2/128);          //RMS amplitude
sampling= 128000000/(b-a1);  // real time sampling frequency

//for   very low or no amplitude, this code wont start
//it takes very small aplitude   of sound to initiate for value sum2-sum1>3, 
//change sum2-sum1 threshold based   on requirement
if(sum2-sum1>3){   
       FFT(128,sampling);        //EasyFFT   based optimised  FFT code
        
             
              for(int   i=0;i<12;i++){in[i]=0;}

int j=0,k=0; //below loop will convert frequency   value to note 
       for(int i=0; i<8;i++)
           {
           if(f_peaks[i]>1040){f_peaks[i]=0;}
            if(f_peaks[i]>=65.4   && f_peaks[i]<=130.8) {f_peaks[i]=255*((f_peaks[i]/65.4)-1);}
            if(f_peaks[i]>=130.8  && f_peaks[i]<=261.6) {f_peaks[i]=255*((f_peaks[i]/130.8)-1);}
            if(f_peaks[i]>=261.6  && f_peaks[i]<=523.25){f_peaks[i]=255*((f_peaks[i]/261.6)-1);}
            if(f_peaks[i]>=523.25 && f_peaks[i]<=1046)  {f_peaks[i]=255*((f_peaks[i]/523.25)-1);}
            if(f_peaks[i]>=1046 && f_peaks[i]<=2093)  {f_peaks[i]=255*((f_peaks[i]/1046)-1);}
            if(f_peaks[i]>255){f_peaks[i]=254;}
           j=1;k=0;
         while(j==1)
               {
              if(f_peaks[i]<=NoteV[k]){f_peaks[i]=k;j=0;}
               k++;  // a note with max peaks (harmonic) with aplitude priority is   selected
              if(k>15){j=0;}
              }

              if(f_peaks[i]==12){f_peaks[i]=0;}
               k=f_peaks[i];
              in[k]=in[k]+(8-i);
             }

k=0;j=0;
           for(int i=0;i<12;i++)
             {
              if(k<in[i]){k=in[i];j=i;}   //Max value detection
             }

          for(int i=0;i<8;i++)
              {
              in[12+i]=in[i];
             }        

for   (int i=0;i<12;i++)
{
  in[20+i]=in[i]*in[i+4]*in[i+7];
  in[32+i]=in[i]*in[i+3]*in[i+7];    //all chord check
}


for (int i=0;i<24;i++)
{
in[i]=in[i+20];
if(k<in[i]){k=in[i];j=i;}    // picking chord with max possiblity
}
char chord_out;
int chord=j;
if(chord>11){chord=chord-12;chord_out='m';}   //Mojor-minor check
else{chord_out=' ';}

// Here "chord" variable has   value of detected chord,
// 0-11 defines all majot chord from C,C#,D,D#,.. B
//12-23   defines all minor chord from Cm,C#m,Dm,D#m,.. Bm

  
   a2=micros();
         k=chord;
        if(k==0){Serial.print('C');Serial.println(chord_out);}
         if(k==1){Serial.print('C');Serial.print('#');Serial.println(chord_out);}
         if(k==2){Serial.print('D');Serial.println(chord_out);}
        if(k==3){Serial.print('D');Serial.print('#');Serial.println(chord_out);}
         if(k==4){Serial.print('E');Serial.println(chord_out);}
        if(k==5){Serial.print('F');Serial.println(chord_out);}
         if(k==6){Serial.print('F');Serial.print('#');Serial.println(chord_out);}
         if(k==7){Serial.print('G');Serial.println(chord_out);}
        if(k==8){Serial.print('G');Serial.print('#');Serial.println(chord_out);}
         if(k==9){Serial.print('A');Serial.println(chord_out);}
        if(k==10){Serial.print('A');Serial.print('#');Serial.println(chord_out);}
         if(k==11){Serial.print('B');Serial.println(chord_out);}
       }
        
}

//-----------------------------FFT Function----------------------------------------------//
//   Documentation on EasyFFT:https://www.instructables.com/member/abhilash_patel/instructables/
//   EasyFFT code optimised for 128 sample size to reduce mamory consumtion

float   FFT(byte N,float Frequency)
{
byte data[8]={1,2,4,8,16,32,64,128};
int   a,c1,f,o,x;
a=N;  
                                 
      for(int i=0;i<8;i++)                  //calculating the levels
         { if(data[i]<=a){o=i;} }
       o=7;
byte in_ps[data[o]]={};     //input for sequencing
float out_r[data[o]]={};    //real part of transform
float out_im[data[o]]={};  //imaginory part of transform
            
x=0;  
      for(int b=0;b<o;b++)                     // bit reversal
          {
          c1=data[b];
          f=data[o]/(c1+c1);
                for(int   j=0;j<c1;j++)
                    { 
                     x=x+1;
                     in_ps[x]=in_ps[j]+f;
                     }
         }
 
      for(int i=0;i<data[o];i++)            //   update input array as per bit reverse order
         {
          if(in_ps[i]<a)
           {out_r[i]=in[in_ps[i]];}
          if(in_ps[i]>a)
          {out_r[i]=in[in_ps[i]-a];}       
         }


int i10,i11,n1;
float e,c,s,tr,ti;

    for(int   i=0;i<o;i++)                                    //fft
    {
     i10=data[i];               // overall values of sine cosine  
     i11=data[o]/data[i+1];     // loop with similar sine cosine
     e=6.283/data[i+1];
     e=0-e;
      n1=0;

          for(int j=0;j<i10;j++)
          {
          c=cos(e*j);   
          s=sin(e*j); 
          n1=j;
          
                for(int   k=0;k<i11;k++)
                 {
                 tr=c*out_r[i10+n1]-s*out_im[i10+n1];
                  ti=s*out_r[i10+n1]+c*out_im[i10+n1];
          
                 out_r[n1+i10]=out_r[n1]-tr;
                  out_r[n1]=out_r[n1]+tr;
          
                 out_im[n1+i10]=out_im[n1]-ti;
                  out_im[n1]=out_im[n1]+ti;          
          
                 n1=n1+i10+i10;
                   }       
             }
     }

/*
for(int i=0;i<data[o];i++)
{
Serial.print(out_r[i]);
Serial.print("\	");                                      // uncomment to print RAW o/p    
Serial.print(out_im[i]);   Serial.println("i");      
}
*/

//---> here onward out_r contains   amplitude and our_in conntains frequency (Hz)
    for(int i=0;i<data[o-1];i++)                // getting amplitude from compex number
        {
         out_r[i]=sqrt((out_r[i]*out_r[i])+(out_im[i]*out_im[i]));   // to  increase the speed delete sqrt
         out_im[i]=(i*Frequency)/data[o];
          /*
         Serial.print(out_im[i],2); Serial.print("Hz");
         Serial.print("\	");                             // uncomment to print freuency bin    
         Serial.println(out_r[i]);   
         */
        }

x=0;       // peak detection
   for(int i=1;i<data[o-1]-1;i++)
       {
      if(out_r[i]>out_r[i-1] && out_r[i]>out_r[i+1]) 
      {in_ps[x]=i;     //in_ps array used for storage of peak number
      x=x+1;}    
      }

s=0;
c=0;
     for(int i=0;i<x;i++)             // re arraange as per magnitude
    {
         for(int j=c;j<x;j++)
        {
            if(out_r[in_ps[i]]<out_r[in_ps[j]])   
                {s=in_ps[i];
                in_ps[i]=in_ps[j];
                in_ps[j]=s;}
         }
    c=c+1;
    }
    
    for(int i=0;i<8;i++)     // updating   f_peak array (global variable)with descending order
    {
     // f_peaks[i]=out_im[in_ps[i]];Serial.println(f_peaks[i]);
      f_peaks[i]=(out_im[in_ps[i]-1]*out_r[in_ps[i]-1]+out_im[in_ps[i]]*out_r[in_ps[i]]+out_im[in_ps[i]+1]*out_r[in_ps[i]+1])
      /(out_r[in_ps[i]-1]+out_r[in_ps[i]]+out_r[in_ps[i]+1]);
     // Serial.println(f_peaks[i]);
     } 
}
    
//------------------------------------------------------------------------------------//

Note detection program

arduino

This program will print the detected note name. Refer the comment within code for clarification.

1//---------------------------------------------------------------------------//
2int  in[128];
3byte NoteV[13]={8,23,40,57,76,96,116,138,162,187,213,241,255}; //data  for note detection based on frequency
4float f_peaks[5]; // top 5 frequencies  peaks in descending order
5int Mic_pin;  
6//---------------------------------------------------------------------------//
7
8
9void  setup() {
10Serial.begin(250000);
11Mic_pin = A7;   // change as per Microphone  pin
12}
13
14
15void loop() 
16{
17  Tone_det();
18
19}
20
21
22//-----------------------------Tone  Detection Function----------------------------------------------//
23// Documentation  on Tone_detection:https://www.instructables.com/member/abhilash_patel/instructables/
24//  Code Written By: Abhilash Patel
25// Contact: abhilashpatel121@gmail.com
26//  This code written for arduino Nano board (should also work for UNO)
27// This code  won't work for any board having RAM less than 2kb,
28
29
30
31void Tone_det()
32{  long unsigned int a1,b,a2;
33  float a;
34  float sum1=0,sum2=0;
35  float sampling;
36  a1=micros();
37        for(int i=0;i<128;i++)
38          {
39            a=analogRead(Mic_pin)-500;     //rough zero shift
40            //utilising time between two sample for windowing  & amplitude calculation
41            sum1=sum1+a;              //to average value
42            sum2=sum2+a*a;            // to RMS value
43            a=a*(sin(i*3.14/128)*sin(i*3.14/128));   // Hann window
44            in[i]=10*a;                // scaling for float  to int conversion
45            delayMicroseconds(195);   // based on operation  frequency range
46          }
47b=micros();
48
49sum1=sum1/128;               //  Average amplitude
50sum2=sqrt(sum2/128);         // RMS
51sampling= 128000000/(b-a1);  // real time sampling frequency
52
53//for very low or no amplitude, this code  wont start
54//it takes very small aplitude of sound to initiate for value sum2-sum1>3,  
55//change sum2-sum1 threshold based on requirement
56if(sum2-sum1>3){  
57       FFT(128,sampling);        
58       //EasyFFT based optimised  FFT code,  
59       //this code updates f_peaks array with 5 most dominent frequency in descending  order
60 
61 for(int i=0;i<12;i++){in[i]=0;}  // utilising in[] array for further  calculation
62
63int j=0,k=0; //below loop will convert frequency value to note  
64       for(int i=0; i<5;i++)
65           {
66           if(f_peaks[i]>1040){f_peaks[i]=0;}
67           if(f_peaks[i]>=65.4   && f_peaks[i]<=130.8) {f_peaks[i]=255*((f_peaks[i]/65.4)-1);}
68           if(f_peaks[i]>=130.8  && f_peaks[i]<=261.6) {f_peaks[i]=255*((f_peaks[i]/130.8)-1);}
69           if(f_peaks[i]>=261.6  && f_peaks[i]<=523.25){f_peaks[i]=255*((f_peaks[i]/261.6)-1);}
70           if(f_peaks[i]>=523.25 && f_peaks[i]<=1046)  {f_peaks[i]=255*((f_peaks[i]/523.25)-1);}
71           if(f_peaks[i]>=1046 && f_peaks[i]<=2093)  {f_peaks[i]=255*((f_peaks[i]/1046)-1);}
72           if(f_peaks[i]>255){f_peaks[i]=254;}
73           j=1;k=0;
74         
75         while(j==1)
76              {
77              if(f_peaks[i]<NoteV[k]){f_peaks[i]=k;j=0;}
78              k++;  // a note with max peaks (harmonic) with aplitude priority is  selected
79              if(k>15){j=0;}
80              }
81
82              if(f_peaks[i]==12){f_peaks[i]=0;}
83              k=f_peaks[i];
84              in[k]=in[k]+(5-i);
85            }
86
87k=0;j=0;
88          for(int i=0;i<12;i++)
89             {
90              if(k<in[i]){k=in[i];j=i;}  //Max value detection
91             }
92       // Note print
93       // if  you need to use note value for some application, use of note number recomendded
94       // where, 0=c;1=c#,2=D;3=D#;.. 11=B;      
95       //a2=micros(); // time  check
96        k=j;
97        if(k==0) {Serial.println('C');}
98        if(k==1)  {Serial.print('C');Serial.println('#');}
99        if(k==2) {Serial.println('D');}
100        if(k==3) {Serial.print('D');Serial.println('#');}
101        if(k==4) {Serial.println('E');}
102        if(k==5) {Serial.println('F');}
103        if(k==6) {Serial.print('F');Serial.println('#');}
104        if(k==7) {Serial.println('G');}
105        if(k==8) {Serial.print('G');Serial.println('#');}
106        if(k==9) {Serial.println('A');}
107        if(k==10){Serial.print('A');Serial.println('#');}
108        if(k==11){Serial.println('B');}
109       }
110}
111
112//-----------------------------FFT  Function----------------------------------------------//
113// Documentation on  EasyFFT:https://www.instructables.com/member/abhilash_patel/instructables/
114//  EasyFFT code optimised for 128 sample size to reduce mamory consumtion
115
116float  FFT(byte N,float Frequency)
117{
118byte data[8]={1,2,4,8,16,32,64,128};
119int  a,c1,f,o,x;
120a=N;  
121                                 
122      for(int i=0;i<8;i++)                 //calculating the levels
123         { if(data[i]<=a){o=i;} }
124      o=7;
125byte in_ps[data[o]]={};     //input for sequencing
126float out_r[data[o]]={};   //real part of transform
127float out_im[data[o]]={};  //imaginory part of transform
128           
129x=0;  
130      for(int b=0;b<o;b++)                     // bit reversal
131         {
132          c1=data[b];
133          f=data[o]/(c1+c1);
134                for(int  j=0;j<c1;j++)
135                    { 
136                     x=x+1;
137                     in_ps[x]=in_ps[j]+f;
138                    }
139         }
140 
141      for(int i=0;i<data[o];i++)            //  update input array as per bit reverse order
142         {
143          if(in_ps[i]<a)
144          {out_r[i]=in[in_ps[i]];}
145          if(in_ps[i]>a)
146          {out_r[i]=in[in_ps[i]-a];}      
147         }
148
149int i10,i11,n1;
150float e,c,s,tr,ti;
151
152    for(int  i=0;i<o;i++)                                    //fft
153    {
154     i10=data[i];              // overall values of sine cosine  
155     i11=data[o]/data[i+1];    // loop with similar sine cosine
156     e=6.283/data[i+1];
157     e=0-e;
158     n1=0;
159
160          for(int j=0;j<i10;j++)
161          {
162          c=cos(e*j);  
163          s=sin(e*j); 
164          n1=j;
165          
166                for(int  k=0;k<i11;k++)
167                 {
168                 tr=c*out_r[i10+n1]-s*out_im[i10+n1];
169                 ti=s*out_r[i10+n1]+c*out_im[i10+n1];
170          
171                 out_r[n1+i10]=out_r[n1]-tr;
172                 out_r[n1]=out_r[n1]+tr;
173          
174                 out_im[n1+i10]=out_im[n1]-ti;
175                 out_im[n1]=out_im[n1]+ti;          
176          
177                 n1=n1+i10+i10;
178                  }       
179             }
180     }
181
182//---> here onward  out_r contains amplitude and our_in conntains frequency (Hz)
183    for(int i=0;i<data[o-1];i++)               // getting amplitude from compex number
184        {
185         out_r[i]=sqrt((out_r[i]*out_r[i])+(out_im[i]*out_im[i]));  // to  increase the speed delete sqrt
186         out_im[i]=(i*Frequency)/data[o];
187         /*
188         Serial.print(out_im[i],2); Serial.print("Hz");
189         Serial.print("\	");                            // uncomment to print freuency bin    
190         Serial.println(out_r[i]);  
191         */
192        }
193
194x=0;       // peak detection
195   for(int i=1;i<data[o-1]-1;i++)
196      {
197      if(out_r[i]>out_r[i-1] && out_r[i]>out_r[i+1]) 
198      {in_ps[x]=i;    //in_ps array used for storage of peak number
199      x=x+1;}    
200      }
201
202s=0;
203c=0;
204    for(int i=0;i<x;i++)             // re arraange as per magnitude
205    {
206        for(int j=c;j<x;j++)
207        {
208            if(out_r[in_ps[i]]<out_r[in_ps[j]])  
209                {s=in_ps[i];
210                in_ps[i]=in_ps[j];
211                in_ps[j]=s;}
212        }
213    c=c+1;
214    }
215    
216    for(int i=0;i<5;i++)     // updating  f_peak array (global variable)with descending order
217     {
218     f_peaks[i]=(out_im[in_ps[i]-1]*out_r[in_ps[i]-1]+out_im[in_ps[i]]*out_r[in_ps[i]]+out_im[in_ps[i]+1]*out_r[in_ps[i]+1])
219     /(out_r[in_ps[i]-1]+out_r[in_ps[i]]+out_r[in_ps[i]+1]);
220     }
221}
222    
223//------------------------------------------------------------------------------------//

//---------------------------------------------------------------------------//
int  in[128];
byte NoteV[13]={8,23,40,57,76,96,116,138,162,187,213,241,255}; //data  for note detection based on frequency
float f_peaks[5]; // top 5 frequencies  peaks in descending order
int Mic_pin;  
//---------------------------------------------------------------------------//


void  setup() {
Serial.begin(250000);
Mic_pin = A7;   // change as per Microphone  pin
}


void loop() 
{
  Tone_det();

}


//-----------------------------Tone  Detection Function----------------------------------------------//
// Documentation  on Tone_detection:https://www.instructables.com/member/abhilash_patel/instructables/
//  Code Written By: Abhilash Patel
// Contact: abhilashpatel121@gmail.com
//  This code written for arduino Nano board (should also work for UNO)
// This code  won't work for any board having RAM less than 2kb,



void Tone_det()
{  long unsigned int a1,b,a2;
  float a;
  float sum1=0,sum2=0;
  float sampling;
  a1=micros();
        for(int i=0;i<128;i++)
          {
            a=analogRead(Mic_pin)-500;     //rough zero shift
            //utilising time between two sample for windowing  & amplitude calculation
            sum1=sum1+a;              //to average value
            sum2=sum2+a*a;            // to RMS value
            a=a*(sin(i*3.14/128)*sin(i*3.14/128));   // Hann window
            in[i]=10*a;                // scaling for float  to int conversion
            delayMicroseconds(195);   // based on operation  frequency range
          }
b=micros();

sum1=sum1/128;               //  Average amplitude
sum2=sqrt(sum2/128);         // RMS
sampling= 128000000/(b-a1);  // real time sampling frequency

//for very low or no amplitude, this code  wont start
//it takes very small aplitude of sound to initiate for value sum2-sum1>3,  
//change sum2-sum1 threshold based on requirement
if(sum2-sum1>3){  
       FFT(128,sampling);        
       //EasyFFT based optimised  FFT code,  
       //this code updates f_peaks array with 5 most dominent frequency in descending  order
 
 for(int i=0;i<12;i++){in[i]=0;}  // utilising in[] array for further  calculation

int j=0,k=0; //below loop will convert frequency value to note  
       for(int i=0; i<5;i++)
           {
           if(f_peaks[i]>1040){f_peaks[i]=0;}
           if(f_peaks[i]>=65.4   && f_peaks[i]<=130.8) {f_peaks[i]=255*((f_peaks[i]/65.4)-1);}
           if(f_peaks[i]>=130.8  && f_peaks[i]<=261.6) {f_peaks[i]=255*((f_peaks[i]/130.8)-1);}
           if(f_peaks[i]>=261.6  && f_peaks[i]<=523.25){f_peaks[i]=255*((f_peaks[i]/261.6)-1);}
           if(f_peaks[i]>=523.25 && f_peaks[i]<=1046)  {f_peaks[i]=255*((f_peaks[i]/523.25)-1);}
           if(f_peaks[i]>=1046 && f_peaks[i]<=2093)  {f_peaks[i]=255*((f_peaks[i]/1046)-1);}
           if(f_peaks[i]>255){f_peaks[i]=254;}
           j=1;k=0;
         
         while(j==1)
              {
              if(f_peaks[i]<NoteV[k]){f_peaks[i]=k;j=0;}
              k++;  // a note with max peaks (harmonic) with aplitude priority is  selected
              if(k>15){j=0;}
              }

              if(f_peaks[i]==12){f_peaks[i]=0;}
              k=f_peaks[i];
              in[k]=in[k]+(5-i);
            }

k=0;j=0;
          for(int i=0;i<12;i++)
             {
              if(k<in[i]){k=in[i];j=i;}  //Max value detection
             }
       // Note print
       // if  you need to use note value for some application, use of note number recomendded
       // where, 0=c;1=c#,2=D;3=D#;.. 11=B;      
       //a2=micros(); // time  check
        k=j;
        if(k==0) {Serial.println('C');}
        if(k==1)  {Serial.print('C');Serial.println('#');}
        if(k==2) {Serial.println('D');}
        if(k==3) {Serial.print('D');Serial.println('#');}
        if(k==4) {Serial.println('E');}
        if(k==5) {Serial.println('F');}
        if(k==6) {Serial.print('F');Serial.println('#');}
        if(k==7) {Serial.println('G');}
        if(k==8) {Serial.print('G');Serial.println('#');}
        if(k==9) {Serial.println('A');}
        if(k==10){Serial.print('A');Serial.println('#');}
        if(k==11){Serial.println('B');}
       }
}

//-----------------------------FFT  Function----------------------------------------------//
// Documentation on  EasyFFT:https://www.instructables.com/member/abhilash_patel/instructables/
//  EasyFFT code optimised for 128 sample size to reduce mamory consumtion

float  FFT(byte N,float Frequency)
{
byte data[8]={1,2,4,8,16,32,64,128};
int  a,c1,f,o,x;
a=N;  
                                 
      for(int i=0;i<8;i++)                 //calculating the levels
         { if(data[i]<=a){o=i;} }
      o=7;
byte in_ps[data[o]]={};     //input for sequencing
float out_r[data[o]]={};   //real part of transform
float out_im[data[o]]={};  //imaginory part of transform
           
x=0;  
      for(int b=0;b<o;b++)                     // bit reversal
         {
          c1=data[b];
          f=data[o]/(c1+c1);
                for(int  j=0;j<c1;j++)
                    { 
                     x=x+1;
                     in_ps[x]=in_ps[j]+f;
                    }
         }
 
      for(int i=0;i<data[o];i++)            //  update input array as per bit reverse order
         {
          if(in_ps[i]<a)
          {out_r[i]=in[in_ps[i]];}
          if(in_ps[i]>a)
          {out_r[i]=in[in_ps[i]-a];}      
         }

int i10,i11,n1;
float e,c,s,tr,ti;

    for(int  i=0;i<o;i++)                                    //fft
    {
     i10=data[i];              // overall values of sine cosine  
     i11=data[o]/data[i+1];    // loop with similar sine cosine
     e=6.283/data[i+1];
     e=0-e;
     n1=0;

          for(int j=0;j<i10;j++)
          {
          c=cos(e*j);  
          s=sin(e*j); 
          n1=j;
          
                for(int  k=0;k<i11;k++)
                 {
                 tr=c*out_r[i10+n1]-s*out_im[i10+n1];
                 ti=s*out_r[i10+n1]+c*out_im[i10+n1];
          
                 out_r[n1+i10]=out_r[n1]-tr;
                 out_r[n1]=out_r[n1]+tr;
          
                 out_im[n1+i10]=out_im[n1]-ti;
                 out_im[n1]=out_im[n1]+ti;          
          
                 n1=n1+i10+i10;
                  }       
             }
     }

//---> here onward  out_r contains amplitude and our_in conntains frequency (Hz)
    for(int i=0;i<data[o-1];i++)               // getting amplitude from compex number
        {
         out_r[i]=sqrt((out_r[i]*out_r[i])+(out_im[i]*out_im[i]));  // to  increase the speed delete sqrt
         out_im[i]=(i*Frequency)/data[o];
         /*
         Serial.print(out_im[i],2); Serial.print("Hz");
         Serial.print("\	");                            // uncomment to print freuency bin    
         Serial.println(out_r[i]);  
         */
        }

x=0;       // peak detection
   for(int i=1;i<data[o-1]-1;i++)
      {
      if(out_r[i]>out_r[i-1] && out_r[i]>out_r[i+1]) 
      {in_ps[x]=i;    //in_ps array used for storage of peak number
      x=x+1;}    
      }

s=0;
c=0;
    for(int i=0;i<x;i++)             // re arraange as per magnitude
    {
        for(int j=c;j<x;j++)
        {
            if(out_r[in_ps[i]]<out_r[in_ps[j]])  
                {s=in_ps[i];
                in_ps[i]=in_ps[j];
                in_ps[j]=s;}
        }
    c=c+1;
    }
    
    for(int i=0;i<5;i++)     // updating  f_peak array (global variable)with descending order
     {
     f_peaks[i]=(out_im[in_ps[i]-1]*out_r[in_ps[i]-1]+out_im[in_ps[i]]*out_r[in_ps[i]]+out_im[in_ps[i]+1]*out_r[in_ps[i]+1])
     /(out_r[in_ps[i]-1]+out_r[in_ps[i]]+out_r[in_ps[i]+1]);
     }
}
    
//------------------------------------------------------------------------------------//

Chord detection program

arduino

1//---------------------------------------------------------------------------//
2int  in[128];
3byte NoteV[13]={8,23,40,57,76,96,116,138,162,187,213,241,255};
4float  f_peaks[8]; // top 8 frequencies peaks in descending order
5//---------------------------------------------------------------------------//
6
7
8void  setup() {
9Serial.begin(250000);
10}
11
12
13void loop() 
14{ 
15  Chord_det();
16
17}
18
19
20//-----------------------------Chord  Detection Function----------------------------------------------//
21// Documentation  on Chord_detection:https://www.instructables.com/member/abhilash_patel/instructables/
22//  Code Written By: Abhilash Patel
23// Contact: abhilashpatel121@gmail.com
24//  this code written for arduino Nano board (should also  work for UNO) or better board
25//  this code won't work for any board having RAM less than 2kb,
26// More accurate  detection can be carried out on more powerful borad by increasing sample size
27
28
29
30void  Chord_det()
31{ 
32  long unsigned int a1,b,a2;
33  float a;
34  float sum1=0,sum2=0;
35  float sampling;
36  a1=micros();
37        for(int i=0;i<128;i++)
38          {
39            a=analogRead(A7)-500;     //rough zero shift
40            //utilising  time between two sample for windowing & amplitude calculation
41            sum1=sum1+a;              //to average value
42            sum2=sum2+a*a;            // to  RMS value
43            a=a*(sin(i*3.14/128)*sin(i*3.14/128));   // Hann window
44            in[i]=4*a;                // scaling for float to int conversion
45            delayMicroseconds(195);   // based on operation frequency range
46          }
47b=micros(); 
48sum1=sum1/128;               //average amplitude
49sum2=sqrt(sum2/128);         //RMS amplitude
50sampling= 128000000/(b-a1);  // real time sampling frequency
51
52//for  very low or no amplitude, this code wont start
53//it takes very small aplitude  of sound to initiate for value sum2-sum1>3, 
54//change sum2-sum1 threshold based  on requirement
55if(sum2-sum1>3){   
56       FFT(128,sampling);        //EasyFFT  based optimised  FFT code
57        
58             
59              for(int  i=0;i<12;i++){in[i]=0;}
60
61int j=0,k=0; //below loop will convert frequency  value to note 
62       for(int i=0; i<8;i++)
63           {
64           if(f_peaks[i]>1040){f_peaks[i]=0;}
65           if(f_peaks[i]>=65.4   && f_peaks[i]<=130.8) {f_peaks[i]=255*((f_peaks[i]/65.4)-1);}
66           if(f_peaks[i]>=130.8  && f_peaks[i]<=261.6) {f_peaks[i]=255*((f_peaks[i]/130.8)-1);}
67           if(f_peaks[i]>=261.6  && f_peaks[i]<=523.25){f_peaks[i]=255*((f_peaks[i]/261.6)-1);}
68           if(f_peaks[i]>=523.25 && f_peaks[i]<=1046)  {f_peaks[i]=255*((f_peaks[i]/523.25)-1);}
69           if(f_peaks[i]>=1046 && f_peaks[i]<=2093)  {f_peaks[i]=255*((f_peaks[i]/1046)-1);}
70           if(f_peaks[i]>255){f_peaks[i]=254;}
71           j=1;k=0;
72         while(j==1)
73              {
74              if(f_peaks[i]<=NoteV[k]){f_peaks[i]=k;j=0;}
75              k++;  // a note with max peaks (harmonic) with aplitude priority is  selected
76              if(k>15){j=0;}
77              }
78
79              if(f_peaks[i]==12){f_peaks[i]=0;}
80              k=f_peaks[i];
81              in[k]=in[k]+(8-i);
82             }
83
84k=0;j=0;
85          for(int i=0;i<12;i++)
86             {
87              if(k<in[i]){k=in[i];j=i;}  //Max value detection
88             }
89
90          for(int i=0;i<8;i++)
91             {
92              in[12+i]=in[i];
93             }        
94
95for  (int i=0;i<12;i++)
96{
97  in[20+i]=in[i]*in[i+4]*in[i+7];
98  in[32+i]=in[i]*in[i+3]*in[i+7];   //all chord check
99}
100
101
102for (int i=0;i<24;i++)
103{
104in[i]=in[i+20];
105if(k<in[i]){k=in[i];j=i;}   // picking chord with max possiblity
106}
107char chord_out;
108int chord=j;
109if(chord>11){chord=chord-12;chord_out='m';}  //Mojor-minor check
110else{chord_out=' ';}
111
112// Here "chord" variable has  value of detected chord,
113// 0-11 defines all majot chord from C,C#,D,D#,.. B
114//12-23  defines all minor chord from Cm,C#m,Dm,D#m,.. Bm
115
116  
117   a2=micros();
118        k=chord;
119        if(k==0){Serial.print('C');Serial.println(chord_out);}
120        if(k==1){Serial.print('C');Serial.print('#');Serial.println(chord_out);}
121        if(k==2){Serial.print('D');Serial.println(chord_out);}
122        if(k==3){Serial.print('D');Serial.print('#');Serial.println(chord_out);}
123        if(k==4){Serial.print('E');Serial.println(chord_out);}
124        if(k==5){Serial.print('F');Serial.println(chord_out);}
125        if(k==6){Serial.print('F');Serial.print('#');Serial.println(chord_out);}
126        if(k==7){Serial.print('G');Serial.println(chord_out);}
127        if(k==8){Serial.print('G');Serial.print('#');Serial.println(chord_out);}
128        if(k==9){Serial.print('A');Serial.println(chord_out);}
129        if(k==10){Serial.print('A');Serial.print('#');Serial.println(chord_out);}
130        if(k==11){Serial.print('B');Serial.println(chord_out);}
131       }
132       
133}
134
135//-----------------------------FFT Function----------------------------------------------//
136//  Documentation on EasyFFT:https://www.instructables.com/member/abhilash_patel/instructables/
137//  EasyFFT code optimised for 128 sample size to reduce mamory consumtion
138
139float  FFT(byte N,float Frequency)
140{
141byte data[8]={1,2,4,8,16,32,64,128};
142int  a,c1,f,o,x;
143a=N;  
144                                 
145      for(int i=0;i<8;i++)                 //calculating the levels
146         { if(data[i]<=a){o=i;} }
147      o=7;
148byte in_ps[data[o]]={};     //input for sequencing
149float out_r[data[o]]={};   //real part of transform
150float out_im[data[o]]={};  //imaginory part of transform
151           
152x=0;  
153      for(int b=0;b<o;b++)                     // bit reversal
154         {
155          c1=data[b];
156          f=data[o]/(c1+c1);
157                for(int  j=0;j<c1;j++)
158                    { 
159                     x=x+1;
160                     in_ps[x]=in_ps[j]+f;
161                    }
162         }
163 
164      for(int i=0;i<data[o];i++)            //  update input array as per bit reverse order
165         {
166          if(in_ps[i]<a)
167          {out_r[i]=in[in_ps[i]];}
168          if(in_ps[i]>a)
169          {out_r[i]=in[in_ps[i]-a];}      
170         }
171
172
173int i10,i11,n1;
174float e,c,s,tr,ti;
175
176    for(int  i=0;i<o;i++)                                    //fft
177    {
178     i10=data[i];              // overall values of sine cosine  
179     i11=data[o]/data[i+1];    // loop with similar sine cosine
180     e=6.283/data[i+1];
181     e=0-e;
182     n1=0;
183
184          for(int j=0;j<i10;j++)
185          {
186          c=cos(e*j);  
187          s=sin(e*j); 
188          n1=j;
189          
190                for(int  k=0;k<i11;k++)
191                 {
192                 tr=c*out_r[i10+n1]-s*out_im[i10+n1];
193                 ti=s*out_r[i10+n1]+c*out_im[i10+n1];
194          
195                 out_r[n1+i10]=out_r[n1]-tr;
196                 out_r[n1]=out_r[n1]+tr;
197          
198                 out_im[n1+i10]=out_im[n1]-ti;
199                 out_im[n1]=out_im[n1]+ti;          
200          
201                 n1=n1+i10+i10;
202                  }       
203             }
204     }
205
206/*
207for(int i=0;i<data[o];i++)
208{
209Serial.print(out_r[i]);
210Serial.print("\	");                                     // uncomment to print RAW o/p    
211Serial.print(out_im[i]);  Serial.println("i");      
212}
213*/
214
215//---> here onward out_r contains  amplitude and our_in conntains frequency (Hz)
216    for(int i=0;i<data[o-1];i++)               // getting amplitude from compex number
217        {
218         out_r[i]=sqrt((out_r[i]*out_r[i])+(out_im[i]*out_im[i]));  // to  increase the speed delete sqrt
219         out_im[i]=(i*Frequency)/data[o];
220         /*
221         Serial.print(out_im[i],2); Serial.print("Hz");
222         Serial.print("\	");                            // uncomment to print freuency bin    
223         Serial.println(out_r[i]);  
224         */
225        }
226
227x=0;       // peak detection
228   for(int i=1;i<data[o-1]-1;i++)
229      {
230      if(out_r[i]>out_r[i-1] && out_r[i]>out_r[i+1]) 
231      {in_ps[x]=i;    //in_ps array used for storage of peak number
232      x=x+1;}    
233      }
234
235s=0;
236c=0;
237    for(int i=0;i<x;i++)             // re arraange as per magnitude
238    {
239        for(int j=c;j<x;j++)
240        {
241            if(out_r[in_ps[i]]<out_r[in_ps[j]])  
242                {s=in_ps[i];
243                in_ps[i]=in_ps[j];
244                in_ps[j]=s;}
245        }
246    c=c+1;
247    }
248    
249    for(int i=0;i<8;i++)     // updating  f_peak array (global variable)with descending order
250    {
251     // f_peaks[i]=out_im[in_ps[i]];Serial.println(f_peaks[i]);
252     f_peaks[i]=(out_im[in_ps[i]-1]*out_r[in_ps[i]-1]+out_im[in_ps[i]]*out_r[in_ps[i]]+out_im[in_ps[i]+1]*out_r[in_ps[i]+1])
253     /(out_r[in_ps[i]-1]+out_r[in_ps[i]]+out_r[in_ps[i]+1]);
254     // Serial.println(f_peaks[i]);
255    } 
256}
257    
258//------------------------------------------------------------------------------------//

//---------------------------------------------------------------------------//
int  in[128];
byte NoteV[13]={8,23,40,57,76,96,116,138,162,187,213,241,255};
float  f_peaks[8]; // top 8 frequencies peaks in descending order
//---------------------------------------------------------------------------//


void  setup() {
Serial.begin(250000);
}


void loop() 
{ 
  Chord_det();

}


//-----------------------------Chord  Detection Function----------------------------------------------//
// Documentation  on Chord_detection:https://www.instructables.com/member/abhilash_patel/instructables/
//  Code Written By: Abhilash Patel
// Contact: abhilashpatel121@gmail.com
//  this code written for arduino Nano board (should also  work for UNO) or better board
//  this code won't work for any board having RAM less than 2kb,
// More accurate  detection can be carried out on more powerful borad by increasing sample size



void  Chord_det()
{ 
  long unsigned int a1,b,a2;
  float a;
  float sum1=0,sum2=0;
  float sampling;
  a1=micros();
        for(int i=0;i<128;i++)
          {
            a=analogRead(A7)-500;     //rough zero shift
            //utilising  time between two sample for windowing & amplitude calculation
            sum1=sum1+a;              //to average value
            sum2=sum2+a*a;            // to  RMS value
            a=a*(sin(i*3.14/128)*sin(i*3.14/128));   // Hann window
            in[i]=4*a;                // scaling for float to int conversion
            delayMicroseconds(195);   // based on operation frequency range
          }
b=micros(); 
sum1=sum1/128;               //average amplitude
sum2=sqrt(sum2/128);         //RMS amplitude
sampling= 128000000/(b-a1);  // real time sampling frequency

//for  very low or no amplitude, this code wont start
//it takes very small aplitude  of sound to initiate for value sum2-sum1>3, 
//change sum2-sum1 threshold based  on requirement
if(sum2-sum1>3){   
       FFT(128,sampling);        //EasyFFT  based optimised  FFT code
        
             
              for(int  i=0;i<12;i++){in[i]=0;}

int j=0,k=0; //below loop will convert frequency  value to note 
       for(int i=0; i<8;i++)
           {
           if(f_peaks[i]>1040){f_peaks[i]=0;}
           if(f_peaks[i]>=65.4   && f_peaks[i]<=130.8) {f_peaks[i]=255*((f_peaks[i]/65.4)-1);}
           if(f_peaks[i]>=130.8  && f_peaks[i]<=261.6) {f_peaks[i]=255*((f_peaks[i]/130.8)-1);}
           if(f_peaks[i]>=261.6  && f_peaks[i]<=523.25){f_peaks[i]=255*((f_peaks[i]/261.6)-1);}
           if(f_peaks[i]>=523.25 && f_peaks[i]<=1046)  {f_peaks[i]=255*((f_peaks[i]/523.25)-1);}
           if(f_peaks[i]>=1046 && f_peaks[i]<=2093)  {f_peaks[i]=255*((f_peaks[i]/1046)-1);}
           if(f_peaks[i]>255){f_peaks[i]=254;}
           j=1;k=0;
         while(j==1)
              {
              if(f_peaks[i]<=NoteV[k]){f_peaks[i]=k;j=0;}
              k++;  // a note with max peaks (harmonic) with aplitude priority is  selected
              if(k>15){j=0;}
              }

              if(f_peaks[i]==12){f_peaks[i]=0;}
              k=f_peaks[i];
              in[k]=in[k]+(8-i);
             }

k=0;j=0;
          for(int i=0;i<12;i++)
             {
              if(k<in[i]){k=in[i];j=i;}  //Max value detection
             }

          for(int i=0;i<8;i++)
             {
              in[12+i]=in[i];
             }        

for  (int i=0;i<12;i++)
{
  in[20+i]=in[i]*in[i+4]*in[i+7];
  in[32+i]=in[i]*in[i+3]*in[i+7];   //all chord check
}


for (int i=0;i<24;i++)
{
in[i]=in[i+20];
if(k<in[i]){k=in[i];j=i;}   // picking chord with max possiblity
}
char chord_out;
int chord=j;
if(chord>11){chord=chord-12;chord_out='m';}  //Mojor-minor check
else{chord_out=' ';}

// Here "chord" variable has  value of detected chord,
// 0-11 defines all majot chord from C,C#,D,D#,.. B
//12-23  defines all minor chord from Cm,C#m,Dm,D#m,.. Bm

  
   a2=micros();
        k=chord;
        if(k==0){Serial.print('C');Serial.println(chord_out);}
        if(k==1){Serial.print('C');Serial.print('#');Serial.println(chord_out);}
        if(k==2){Serial.print('D');Serial.println(chord_out);}
        if(k==3){Serial.print('D');Serial.print('#');Serial.println(chord_out);}
        if(k==4){Serial.print('E');Serial.println(chord_out);}
        if(k==5){Serial.print('F');Serial.println(chord_out);}
        if(k==6){Serial.print('F');Serial.print('#');Serial.println(chord_out);}
        if(k==7){Serial.print('G');Serial.println(chord_out);}
        if(k==8){Serial.print('G');Serial.print('#');Serial.println(chord_out);}
        if(k==9){Serial.print('A');Serial.println(chord_out);}
        if(k==10){Serial.print('A');Serial.print('#');Serial.println(chord_out);}
        if(k==11){Serial.print('B');Serial.println(chord_out);}
       }
       
}

//-----------------------------FFT Function----------------------------------------------//
//  Documentation on EasyFFT:https://www.instructables.com/member/abhilash_patel/instructables/
//  EasyFFT code optimised for 128 sample size to reduce mamory consumtion

float  FFT(byte N,float Frequency)
{
byte data[8]={1,2,4,8,16,32,64,128};
int  a,c1,f,o,x;
a=N;  
                                 
      for(int i=0;i<8;i++)                 //calculating the levels
         { if(data[i]<=a){o=i;} }
      o=7;
byte in_ps[data[o]]={};     //input for sequencing
float out_r[data[o]]={};   //real part of transform
float out_im[data[o]]={};  //imaginory part of transform
           
x=0;  
      for(int b=0;b<o;b++)                     // bit reversal
         {
          c1=data[b];
          f=data[o]/(c1+c1);
                for(int  j=0;j<c1;j++)
                    { 
                     x=x+1;
                     in_ps[x]=in_ps[j]+f;
                    }
         }
 
      for(int i=0;i<data[o];i++)            //  update input array as per bit reverse order
         {
          if(in_ps[i]<a)
          {out_r[i]=in[in_ps[i]];}
          if(in_ps[i]>a)
          {out_r[i]=in[in_ps[i]-a];}      
         }


int i10,i11,n1;
float e,c,s,tr,ti;

    for(int  i=0;i<o;i++)                                    //fft
    {
     i10=data[i];              // overall values of sine cosine  
     i11=data[o]/data[i+1];    // loop with similar sine cosine
     e=6.283/data[i+1];
     e=0-e;
     n1=0;

          for(int j=0;j<i10;j++)
          {
          c=cos(e*j);  
          s=sin(e*j); 
          n1=j;
          
                for(int  k=0;k<i11;k++)
                 {
                 tr=c*out_r[i10+n1]-s*out_im[i10+n1];
                 ti=s*out_r[i10+n1]+c*out_im[i10+n1];
          
                 out_r[n1+i10]=out_r[n1]-tr;
                 out_r[n1]=out_r[n1]+tr;
          
                 out_im[n1+i10]=out_im[n1]-ti;
                 out_im[n1]=out_im[n1]+ti;          
          
                 n1=n1+i10+i10;
                  }       
             }
     }

/*
for(int i=0;i<data[o];i++)
{
Serial.print(out_r[i]);
Serial.print("\	");                                     // uncomment to print RAW o/p    
Serial.print(out_im[i]);  Serial.println("i");      
}
*/

//---> here onward out_r contains  amplitude and our_in conntains frequency (Hz)
    for(int i=0;i<data[o-1];i++)               // getting amplitude from compex number
        {
         out_r[i]=sqrt((out_r[i]*out_r[i])+(out_im[i]*out_im[i]));  // to  increase the speed delete sqrt
         out_im[i]=(i*Frequency)/data[o];
         /*
         Serial.print(out_im[i],2); Serial.print("Hz");
         Serial.print("\	");                            // uncomment to print freuency bin    
         Serial.println(out_r[i]);  
         */
        }

x=0;       // peak detection
   for(int i=1;i<data[o-1]-1;i++)
      {
      if(out_r[i]>out_r[i-1] && out_r[i]>out_r[i+1]) 
      {in_ps[x]=i;    //in_ps array used for storage of peak number
      x=x+1;}    
      }

s=0;
c=0;
    for(int i=0;i<x;i++)             // re arraange as per magnitude
    {
        for(int j=c;j<x;j++)
        {
            if(out_r[in_ps[i]]<out_r[in_ps[j]])  
                {s=in_ps[i];
                in_ps[i]=in_ps[j];
                in_ps[j]=s;}
        }
    c=c+1;
    }
    
    for(int i=0;i<8;i++)     // updating  f_peak array (global variable)with descending order
    {
     // f_peaks[i]=out_im[in_ps[i]];Serial.println(f_peaks[i]);
     f_peaks[i]=(out_im[in_ps[i]-1]*out_r[in_ps[i]-1]+out_im[in_ps[i]]*out_r[in_ps[i]]+out_im[in_ps[i]+1]*out_r[in_ps[i]+1])
     /(out_r[in_ps[i]-1]+out_r[in_ps[i]]+out_r[in_ps[i]+1]);
     // Serial.println(f_peaks[i]);
    } 
}
    
//------------------------------------------------------------------------------------//

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signal pin from module need to be connected to any analog pin of arduino. required change to be made on code accordingly.

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