Theremino. Code for a custom Ardunio based instrument I designed.

therem.ino

#define trigPin 13
#define echoPin 12
#define tonePin 8
#define ledPin 7
#define keyPin 0

#include "notes.h"

const int threshold = 200;
int notes[] = { NOTE_B0,NOTE_C1,NOTE_CS1,NOTE_D1,NOTE_DS1,NOTE_E1,NOTE_F1,NOTE_FS1,NOTE_G1,NOTE_GS1,NOTE_A1,NOTE_AS1,NOTE_B1,NOTE_C2,NOTE_CS2,NOTE_D2,NOTE_DS2,NOTE_E2,NOTE_F2,NOTE_FS2,NOTE_G2,NOTE_GS2,NOTE_A2, NOTE_AS2,NOTE_B2, NOTE_C3, NOTE_CS3,NOTE_D3, NOTE_DS3,NOTE_E3, NOTE_F3, NOTE_FS3,NOTE_G3, NOTE_GS3,NOTE_A3, NOTE_AS3,NOTE_B3, NOTE_C4, NOTE_CS4,NOTE_D4, NOTE_DS4,NOTE_E4, NOTE_F4, NOTE_FS4,NOTE_G4, NOTE_GS4,NOTE_A4, NOTE_AS4,NOTE_B4, NOTE_C5, NOTE_CS5,NOTE_D5, NOTE_DS5,NOTE_E5, NOTE_F5, NOTE_FS5,NOTE_G5, NOTE_GS5,NOTE_A5, NOTE_AS5,NOTE_B5, NOTE_C6,  NOTE_CS6, NOTE_D6,  NOTE_DS6, NOTE_E6,  NOTE_F6,  NOTE_FS6, NOTE_G6,  NOTE_GS6, NOTE_A6,  NOTE_AS6, NOTE_B6,  NOTE_C7,  NOTE_CS7, NOTE_D7,  NOTE_DS7, NOTE_E7,  NOTE_F7,  NOTE_FS7, NOTE_G7,  NOTE_GS7, NOTE_A7,  NOTE_AS7, NOTE_B7,  NOTE_C8,  NOTE_CS8, NOTE_D8,  NOTE_DS8 };

void setup() {
  Serial.begin (9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  long duration, distance;
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = (duration/2) / 29.1;
  
  int sensorReading = analogRead(keyPin);

  if (sensorReading > threshold){
    int pitchIndex = (distance / 4) + 24;
    int pitch = notes[pitchIndex];
    tone(tonePin, pitch);
    Serial.print(pitch);
    Serial.println(" hz");
    digitalWrite(ledPin, HIGH);
  }
  else {
    digitalWrite(ledPin, LOW);
    noTone(tonePin);
  }
  delay(10);
}