bool a;
bool b;
bool c;
bool d;
void setup() {
  // put your setup code here, to run once:
pinMode(2, OUTPUT);
pinMode(3, INPUT_PULLUP);
pinMode(4, INPUT_PULLUP);
pinMode(5, INPUT_PULLUP);
pinMode(6, INPUT_PULLUP);
}

void loop() {
 a=digitalRead(3);
 b=digitalRead(4);
 c=digitalRead(5);
 d=digitalRead(6);
 if (a==LOW)
 {tone(2,261);
 delay(1000);
 noTone(2);}

  if (b==LOW)
 {tone(2,294);
 delay(1000);
 noTone(2);}

  if (c==LOW)
 {tone(2,330);
 delay(1000);
 noTone(2);}

  if (d==LOW)
 {tone(2,349);
 delay(1000);
 noTone(2);}

}