Sure you can use LDR's, potentiometers and buttons to generate sounds, but what about strings?

When I began thinking about an Arduino string instrument, I realized what I wanted to create was a soft potentiometer. I found my inspiration from Hannah Perner-Wilson's Fabric Potentiometer http://www.kobakant.at/DIY/?p=543.

String Instrument from mizliz on Vimeo.

Step 1: Parts

Arduino Microcontroller
3.3Ω resistor (1 per string)
Conductive thread Lame Lifesaver Lamé Lifesaver
Nickel/Copper/Cobalt Fabric Tape http://www.lessemf.com/fabric.html
8Ω speaker (1 per string)
Solderless breadboard
22-AWG hookup wire
30-AWG wire (optional)
Wooden Dowel
Metal nails or small screw eyes
Drill
Saw
Needle
Scissors
Wire Stripper
Pencil or marker
Box

Step 2: How It Works

Each string is basically a potentiometer that controls the sound of a speaker.

Step 3: Building the Instrument

1. Cut two pieces of a wooden dowel. Your length is determined by how long you want your bridge to be. The dowels purpose here is to keep the strings away from your GND.

2.Mark where you want to drill holes on your dowels. Remember, you want to keep the strings off your GND. You should drill holes so that when you string the instrument the strings are parallel to each other.

3.Using a glue gun, fix your dowel onto your box.

4. Either drill holes for nails or screws on the outer side of your dowels or solder 30 AWG wire to eye screws and thread them through the dowels. If you are doing the the eye screws, one side goes to the analog pins, the other goes to power through a 3.3Ω resistor. I used red wires on one side to go to power and yellow wires to go to the analog pins. For the demo version the alligator clips attach to one nail connecting together an analog input and power through a resistor.

Step 4: Making Connections

1. You'll have to figure out a way to connect the tape to GND on the Arduino. One option is to use alligator clips. Another is to use brads and solder them together on the inside.

2. Using the conductive thread on a needle, attach the conductive thread to the screws or nails. Tightly string the threads across. Weave the thread across at least twice. Use one string to attach all the nails or screws.

3. Connect one nail or screw to power through the 3.3Ω resistor .

4. Connect one nail or screw to an analog pin.

4. Attach at least one 8Ω speaker through a 100Ω resistor to a digital pin.

5. Create a pick or bow. It can be anything as long as it is conductive.

Step 5: The Tone Library

The Tone Library can be used to produce square-waves of the specified frequency on any Arduino pin. You can set the duration of the sound or use the method stop() to stop the sound.

To play a tone, connect a pin to a piezo buzzer or a speaker.

For this demo, I used a 8Ω speaker connected to pin 7 through a 100Ω resistor.

To use the library, you need to instantiate an instance of Tone:

	#include <Tone.h>

Tone notePlayer;

void setup(void){
     //the number reflects the speaker pin
     notePlayer.begin(7);
}
void loop(){
     //To play a note:
     notePlayer.play(NOTE_B3);
}

These are the methods that you can use with this Library:

begin() - prepares a pin for playing a tone.
isPlaying() - returns true if tone is playing, false if not.
play() - play a tone.
stop() - stop playing a tone.

This is a list of constant values of frequencies for notes:

Constant Name	Frequency (Hz)
NOTE_B2	123
NOTE_C3	131
NOTE_CS3	139
NOTE_D3	147
NOTE_DS3	156
NOTE_E3	165
NOTE_F3	175
NOTE_FS3	185
NOTE_G3	196
NOTE_GS3	208
NOTE_A3	220
NOTE_AS3	233
NOTE_B3	247
NOTE_C4	262
NOTE_CS4	277
NOTE_D4	294
NOTE_DS4	311
NOTE_E4	330
NOTE_F4	349
NOTE_FS4	370
NOTE_G4	392
NOTE_GS4	415
NOTE_A4	440
NOTE_AS4	466
NOTE_B4	494
NOTE_C5	523
NOTE_CS5	554
NOTE_D5	587
NOTE_DS5	622
NOTE_E5	659
NOTE_F5	698
NOTE_FS5	740
NOTE_G5	784
NOTE_GS5	831
NOTE_A5	880
NOTE_AS5	932
NOTE_B5	988
NOTE_C6	1047
NOTE_CS6	1109
NOTE_D6	1175
NOTE_DS6	1245
NOTE_E6	1319
NOTE_F6	1397
NOTE_FS6	1480
NOTE_G6	1568
NOTE_GS6	1661
NOTE_A6	1760
NOTE_AS6	1865
NOTE_B6	1976
NOTE_C7	2093
NOTE_CS7	2217
NOTE_D7	2349
NOTE_DS7	2489
NOTE_E7	2637
NOTE_F7	2794
NOTE_FS7	2960
NOTE_G7	3136
NOTE_GS7	3322
NOTE_A7	3520
NOTE_AS7	3729
NOTE_B7	3951
NOTE_C8	4186
NOTE_CS8	4435
NOTE_D8	4699
NOTE_DS8	4978

More information can be found here:ToneLibraryDocumentation

Step 6: Putting It Altogether

Here is code for a two speaker instrument:

	#include <Tone.h>


int potValue;
int potValue2;

Tone speaker[2];
int notes[] = { 
  NOTE_A3,
  NOTE_B3,
  NOTE_C4,
  NOTE_D4,
  NOTE_E4,
  NOTE_F4,
  NOTE_G4,
  NOTE_A4,
  NOTE_B4,
  NOTE_C5,
  NOTE_D5,
  NOTE_E5,
  NOTE_F5,
  NOTE_G5,
  NOTE_A5,
  NOTE_B5,
  NOTE_C6};
void setup() {
  // initialize serial communications at 9600 bps:
  Serial.begin(9600); 
  speaker[0].begin(7);
  speaker[1].begin(8);
}
void loop() {

  potValue = analogRead(A0);   // read the pot value
 
 Serial.println(potValue);
 if (potValue<100){
    speaker[0].play(notes[0]);
     speaker[1].play(notes[12]);
  } 
  else if (potValue<200){
    speaker[0].play(notes[1]);
    speaker[1].play(notes[11]);
  }
  else if (potValue<250){
    speaker[0].play(notes[2]);
    speaker[1].play(notes[10]);
  }
  else if (potValue<320){
    speaker[0].play(notes[3]);
    speaker[1].play(notes[9]);
  }
  else if (potValue<400){
    speaker[0].play(notes[4]);
    speaker[1].play(notes[8]);
  }
  else if (potValue<450){
    speaker[0].play(notes[5]);
    speaker[1].play(notes[7]);
  }
  else if (potValue<500){
    speaker[0].play(notes[6]);
    speaker[1].play(notes[4]);
  }
  else if (potValue<550){
    speaker[0].play(notes[7]);
    speaker[1].play(notes[3]);
  }
  else if (potValue<700){
    speaker[0].play(notes[8]);
    speaker[1].play(notes[2]);
  }
  else if (potValue<900){
    speaker[0].play(notes[9]);
    speaker[1].play(notes[1]);
  }
  else{
    speaker[0].stop();
    speaker[1].stop();
  }