int ledOn[4] = {}; 
float time[4] = {0, 0, 0, 0};

void setup() {
  // put your setup code here, to run once:
  pinMode(2, INPUT_PULLUP);
  pinMode(3, INPUT_PULLUP);
  pinMode(4, INPUT_PULLUP);
  pinMode(5, INPUT_PULLUP);

  pinMode(7, OUTPUT);

  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);

}

void loop() {
  // put your main code here, to run repeatedly:
  for (int i = 2; i < 6 ; i ++) {
      if(digitalRead(i) == LOW) {
        digitalWrite(i + 6, HIGH);
        tone(7, i * 1000);
        time[i-2] = millis();
      }
  }

  for(int i = 2; i < 6; i ++) {
    if (millis() - time[i-2] >= 500) {
      noTone(7);
      digitalWrite(i + 6, LOW);
    }
  }

}