#include "pitches.h"

volatile bool enableNoteA3 = false;
volatile bool enableNoteG3 = false;

void setup() {

  pinMode(18 ,INPUT);
  pinMode(21 ,INPUT);
  
  attachInterrupt(digitalPinToInterrupt(18), toggleA3, RISING);
  attachInterrupt(digitalPinToInterrupt(21), toggleG3, RISING);
}

void loop() {
  if (enableNoteA3) {
    tone(8, NOTE_A3, 1000);
  }
  if (enableNoteG3) {
    tone(8, NOTE_G3, 1000);
  }
  if (!(enableNoteA3 || enableNoteG3)) {
    noTone(8);
  }
}

void toggleA3() {
  enableNoteA3 = !enableNoteA3;
}

void toggleG3() {
  enableNoteG3 = !enableNoteG3;
}