Arduino Rainbow Hack. Mash up of http://ardx.org/CODE12S and http://www.arduino.cc/en/Tutorial/Melody

Arduino Rainbow Hack

// Piezo speaker connected to pins
int speakerPin = 6;
// RGB LED leads connected to PWM pins
const int RED_LED_PIN = 9;
const int GREEN_LED_PIN = 10;
const int BLUE_LED_PIN = 11;

// Used to store the current intensity level of the individual LEDs
int redIntensity = 0;
int greenIntensity = 0;
int blueIntensity = 0;

char notes[] = {"cCbgabccaag "}; // a space represents a rest
int length = sizeof(notes); // the number of notes
int beats[] = {4,4,2,1,1,2,4,1,1,1,4,1};
int tempo = 300;

void playTone(int tone, int duration) {
  for (long i = 0; i < duration * 1000L; i += tone * 2) {
    digitalWrite(speakerPin, HIGH);
    delayMicroseconds(tone);
    digitalWrite(speakerPin, LOW);
    delayMicroseconds(tone);
  }
}

void playNote(char note, int duration) {
char names[] = { 'c', 'l', 'd', 'm','e', 'f', 'n', 'g', 'o','a', 'p', 'b', 'C', 'L', 'D', 'M', 'E', 'F', 'N', 'G', 'O', 'A', 'P', 'B' };
int tones[] = { 1915, 1805, 1700, 1608, 1519, 1432, 1351, 1275, 1205, 1136, 1073, 1014, 956, 903, 850, 804, 760, 716, 676, 638, 603, 568, 478 };
  
  // play the tone corresponding to the note name
  for (int i = 0; i < sizeof(names); i++) {
    if (names[i] == note) {
      playTone(tones[i], duration);
    }
  }
}

void setup() {
  pinMode(speakerPin, OUTPUT);
}

void loop() {
  for (int i = 0; i < length; i++) {
    if (notes[i] == ' ') {
      delay(beats[i] * tempo); // rest
    } else {
      playNote(notes[i], beats[i] * tempo);
      greenIntensity = 255 * rand();
      redIntensity = 255 * rand();
      blueIntensity = 255 * rand();
      analogWrite(GREEN_LED_PIN, greenIntensity);
      analogWrite(RED_LED_PIN, redIntensity);
      analogWrite(BLUE_LED_PIN, blueIntensity);
      delay(beats[i]);
    }
    
    // pause between notes
    delay(tempo / 2); 
  }
}