#include "pitches.h"

int SPEAKER_PIN = 8;

int buttonPins[] = { 12, 11, 10, 9, 7, 6, 5, 4 };
int buttonTones[] = {
  NOTE_C4, NOTE_D4, NOTE_E4, NOTE_F4,
  NOTE_G4, NOTE_A4, NOTE_B4, NOTE_C5
};

void setup() {
  for (uint8_t i = 0; i < 8; i++)
    pinMode(buttonPins[i], INPUT_PULLUP);
  pinMode(SPEAKER_PIN, OUTPUT);
}

void loop() {
  for (uint8_t i = 0; i < 8; i++)
    if (digitalRead(buttonPins[i]) == LOW)
      tone(SPEAKER_PIN, buttonTones[i], 100);
}