int but1 = D4;
int but2 = D5;
int but3 = D7;
int but4 = D8;
int but5 = D9;
int buzzer = D6;

void setup() {
  pinMode(but1, INPUT);
  pinMode(but2, INPUT);
  pinMode(but3, INPUT);
  pinMode(but4, INPUT);
  pinMode(but5, INPUT); 
  pinMode(buzzer, OUTPUT);
}

void loop() {
  int b1 = digitalRead(but1);
  int b2 = digitalRead(but2);
  int b3 = digitalRead(but3);
  int b4 = digitalRead(but4);
  int b5 = digitalRead(but5);

  if (b1 == 1) tone(buzzer, 200, 100);
  if (b2 == 1) tone(buzzer, 400, 100);
  if (b3 == 1) tone(buzzer, 500, 100);
  if (b4 == 1) tone(buzzer, 600, 100);
  if (b5 == 1) tone(buzzer, 700, 100);

  delay(10);
}