Hey there, I have built an instrument that I dreamt up, and am trying to write the code that would allow me to play the instrument as I see fit. I'm calling it a Victorian Synthesizer.
The arduino board and 1/4" out is mounted underneath the platter, and there are 5 FSR's underneath the silver foil layer underneath each shell, so pressing the shell controls the value read by the analog inputs.
I have written out the code as much as I can understand, and I know that it needs some tweaking in order for it to work properly. I would truly appreciate any advice that you may have for how to get it up and running properly.
I am pretty well versed in analog audio circuits, and plan on building some sort of VCF to help make the output sound nicer than just a square wave....i've been doing research on how to produce a rough sine wave out of square waves, but that will be a different topic 
for now, i'm just trying to get the code up and running.
The wiring is just 5 FSR's hooked up as voltage dividers going into the analog ins.
The four shells on the top will play the root note for a chord, and the shell at the bottom will play the corresponding scale depending on which root note is chosen
Here's the code I have written. It compiles but is not fully efficient:
//Victorian Synth Attempts.
//analog in 0-4 and audio out on digital 3
//define analog inputs
#define SCALE_KEY (0)
#define C1_KEY (1)
#define Gs1_KEY (2)
#define D1_KEY (3)
#define G1_KEY (4)
void setup() {
Serial.begin(9600); //might use the serial monitor once this is up and running
pinMode (3,OUTPUT); //Audio Out pin
}
void loop() {
// int C1_KEYread = analogRead (A1);
// int Gs1_KEYread = analogRead (A2);
// int D1_KEYread = analogRead (A3);
// int G1_KEYread = analogRead (A4);
int AudioOut = 3;
AudioOut = analogRead(SCALE_KEY); //Play the SCALE Key through digital out pin 3
//mapped notes
int mapC1[] = {98,117,131,165,196,233,262,330,392,466,523,659,784,932,
1175,1319,1568,1865
};
int mapGs1[] = {65,78,104,131,156,208,262,311,415,523,622,831,1047,1245,
1661,2093
};
int mapD1[] = {39,44,49,52,58,65,73,78,87,98,104,117,131,147,156,175,196,
208,233,262,294,311,349,392,415,466,523,587,622,698,784,831,932,
1047,1175,1245,1397,1568,1661,1865,2093,2349
};
int mapG1[] = {65,82,98,117,131,165,196,233,262,330,392,466,523,659,784,
932,1175,1319,1568,1865
};
// mapped scale to play is dependent upon which key is being pressed
digitalRead(C1_KEY); //check the state of C1 Key
digitalRead(Gs1_KEY); //check the state of Gs1 Key
digitalRead(D1_KEY); //check the state of D1 Key
digitalRead(G1_KEY); //check the state of G1 Key
if (C1_KEY < 5) { //if C1 Key is being pressed...(5 was just chosen, can be anything above 0 really)
tone(3,33); //play the root note C1 constantly while C1 key is pressed
int mapC1(analogRead(SCALE_KEY)); //play the C1 scale on the Scale Key
}
else {
if (Gs1_KEY < 5) { //if Gs1 Key is pressed
tone(3,52); //play the root note Gs1 constantly while D1 key is pressed
int mapGs1(analogRead(SCALE_KEY)); //play the Gs1 scale on the Scale Key
}
else {
if (D1_KEY < 5) { //if D1 Key is pressed
tone(3,37); //play the root note D1 constantly while D1 key is pressed
int mapD1(analogRead(SCALE_KEY)); //play the D1 scale on the Scale key
}
else {
if (G1_KEY < 5) { //if G1 Key is pressed
tone(3,49); //play the root note G1 constantly while G1 key is pressed
int mapG1(analogRead(SCALE_KEY));
}
}
}
}
}
Here's the Chart that states the Note recognized through the library pitches.h as well as the number value. I just used the number value instead of including the library.
C1 33 <--ROOT
G2 98 <--Corresponding Scale
As2 117
C3 131
E3 165
G3 196
As3 233
C4 262
E4 330
G4 392
As4 466
C5 523
E5 659
G5 784
As5 932
C6 1175
E6 1319
G6 1568
As6 1865
Gs1 52 <--ROOT
C2 65 <---corresponding scale
Ds2 78
Gs2 104
C3 131
Ds3 156
Gs3 208
C4 262
Ds4 311
Gs4 415
C5 523
Ds5 622
Gs5 831
C6 1047
Ds6 1245
Gs6 1661
C7 2093
D1 37 <--ROOT
Ds1 39 <---corresponding scale
F1 44
G1 49
Gs1 52
As1 58
C2 65
D2 73
Ds2 78
F2 87
G2 98
Gs2 104
As2 117
C3 131
D3 147
Ds3 156
F3 175
G3 196
Gs3 208
As3 233
C4 262
D4 294
Ds4 311
F4 349
G4 392
Gs4 415
As4 466
C5 523
D5 587
Ds5 622
F5 698
G5 784
Gs5 831
As5 932
C6 1047
D6 1175
Ds6 1245
F6 1397
G6 1568
Gs6 1661
As6 1865
C7 2093
D7 2349
G1 49 <--ROOT
C2 65 <--Corresponding Scale
E2 82
G2 98
As2 117
C3 131
E3 165
G3 196
As3 233
C4 262
E4 330
G4 392
As4 466
C5 523
E5 659
G5 784
As5 932
C6 1175
E6 1319
G6 1568
As6 1865
Thank you so much for any assistance you may be able to provide.