#include "pitches.h"
#define SPEAKER_PIN 8
int btnPins[] = { 12, 11, 10, 9, 7, 6, 5, 4 };
const int btnTones[] = {
  NOTE_C4, NOTE_D4, NOTE_E4, NOTE_F4,
  NOTE_G4, NOTE_A4, NOTE_B4, NOTE_C5
};
const int n = sizeof(btnPins) / sizeof(btnPins[0]);

void setup() {
  for(int i=0;i<n;i++){
    pinMode(btnPins[i], INPUT_PULLUP);
  }

  pinMode(SPEAKER_PIN, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:2
  int pitch = 0;
  for (int i = 0; i < n; i++) {
    if (digitalRead(btnPins[i]) == LOW) {
      pitch = btnTones[i];
    }
  }
  if (pitch) {
    tone(SPEAKER_PIN, pitch);
  } else {
    noTone(SPEAKER_PIN);
  }
}