int value = 0;
void setup() {
  pinMode(11, INPUT_PULLUP);
  pinMode(10, INPUT_PULLUP);
  pinMode(9, INPUT_PULLUP);
  pinMode(8, INPUT_PULLUP);
  pinMode(12, OUTPUT);
}

void loop() {
  tone(12, value);
  if(digitalRead(11)==LOW){
    delay(100);
    value = 500;
  }
  if(digitalRead(10)==LOW){
    delay(100);
    value = 1000;
  }
  if(digitalRead(9)==LOW){
    delay(100);
    value = 1500;
  }
  if(digitalRead(8)==LOW){
    delay(100);
    value = 2000;
  }
}