Piezo melody on an Arduino Uno

// Melody: a tune on a piezo, one note at a time, with a lamp on the beat.
//
//   pin 8   a passive piezo, its other leg to GND
//   pin 13  the lamp, through 220 ohm to GND
//
// tone(pin, frequency) starts a square wave on the pin from timer 2 and
// returns at once, so the sketch decides how long a note lasts with its own
// delay() and stops it with noTone(). The gap after each note is what makes
// two notes of the same pitch sound like two notes instead of one long one.
//
// The tune is the opening of Beethoven's "Ode to Joy", which is old enough
// to belong to everybody. Each note is a frequency in hertz and a length in
// beats; change TEMPO_MS to play it faster or slower, or write your own.

const int PIEZO = 8;
const int LAMP = 13;

// The notes the tune needs, in hertz (A4 is 440).
const unsigned int C4 = 262;
const unsigned int D4 = 294;
const unsigned int E4 = 330;
const unsigned int F4 = 349;
const unsigned int G4 = 392;

const unsigned int NOTES[] = {
  E4, E4, F4, G4, G4, F4, E4, D4, C4, C4, D4, E4, E4, D4, D4,
};
// Length in beats, times two, so a half beat is 1 and a beat and a half is 3.
const unsigned char BEATS[] = {
  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 1, 4,
};
const int COUNT = sizeof(BEATS);

const unsigned long TEMPO_MS = 200;  // half a beat
const unsigned long GAP_MS = 30;     // the silence between notes

void setup() {
  pinMode(LAMP, OUTPUT);
  Serial.begin(115200);
  Serial.println("Mokxi Arduino Uno: melody on pin 8");
}

void loop() {
  for (int i = 0; i < COUNT; i++) {
    unsigned long length = TEMPO_MS * BEATS[i];
    Serial.print("note ");
    Serial.print(NOTES[i]);
    Serial.println(" Hz");
    digitalWrite(LAMP, HIGH);
    tone(PIEZO, NOTES[i]);
    delay(length - GAP_MS);
    noTone(PIEZO);
    digitalWrite(LAMP, LOW);
    delay(GAP_MS);
  }
  Serial.println("again in two seconds");
  delay(2000);
}