keyboard by Tom Igoe

Plays a pitch that changes based on a changing analog input circuit: 3 force-sensing resistors from +5V to analog in 0 through 5 3 10K resistors from analog in 0 through 5 to ground 8-ohm speaker on digital pin 8

const int threshold = 10; // minimum reading of the sensors that generates a note

// notes to play, corresponding to the 3 sensors:
int notes[] = { NOTE_A4, NOTE_B4, NOTE_C3 };

void setup()
{
}

void loop()
{
  for (int thisSensor = 0; thisSensor < 3; thisSensor++)
  {
    // get a sensor reading:
    int sensorReading = analogRead(thisSensor);

    // if the sensor is pressed hard enough:
    if (sensorReading > threshold)
    {
      // play the note corresponding to this sensor:
      tone(8, notes[thisSensor], 20);
    }
  }
  Serial.println();
}