// P04-B: Piano 4 nada dengan tone()
const int BUZZER = 8;
const int TOMBOL[] = {4, 5, 6, 7};
const int NADA[]   = {262, 294, 330, 392};  // Do Re Mi Sol (Hz)

void setup() {
  for (int i = 0; i < 4; i++)
    pinMode(TOMBOL[i], INPUT_PULLUP);
  pinMode(BUZZER, OUTPUT);
}

void loop() {
  bool adaNada = false;
  for (int i = 0; i < 4; i++) {
    if (digitalRead(TOMBOL[i]) == LOW) {
      tone(BUZZER, NADA[i]);
      adaNada = true;
    }
  }
  if (!adaNada) noTone(BUZZER);
}