#define BUZZER_PIN 2

const uint8_t buttonPins[] = { 3, 4, 5, 6, 7, 8};

const int buttonFrequencies[] = { 250, 300, 350, 400, 450, 500 };

const int numTones = sizeof(buttonPins) / sizeof(buttonPins[0]);

void setup() {
  for (uint8_t i = 0; i < numTones; i++) {
    pinMode(buttonPins[i], INPUT_PULLUP);
  }
  pinMode(BUZZER_PIN, OUTPUT);
}

void loop() {
  int frequency = 0;
  for (uint8_t i = 0; i < numTones; i++) {
    if (digitalRead(buttonPins[i]) == LOW) {
      frequency = buttonFrequencies[i];
    }
  }
  if (frequency) {
    tone(BUZZER_PIN, frequency);
  } else {
    noTone(BUZZER_PIN);
  }
}