const int buttonPin = A2;
const int buzzerPin = 10;
int toneFrequency = 100; // in Hz

void setup() {
  pinMode(buttonPin, INPUT_PULLUP); // button input, using internal pull-up resistor
  pinMode(buzzerPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // Button is active LOW due to INPUT_PULLUP
  if (digitalRead(buttonPin) == LOW) {
    toneFrequency++;
    tone(buzzerPin, toneFrequency);
    Serial.println(toneFrequency);
    if(toneFrequency == 0) {
      toneFrequency = 1;
    }
  } else {;
    tone(buzzerPin, toneFrequency);
    toneFrequency--;
        Serial.println(toneFrequency);
if(toneFrequency == 0) {
      toneFrequency = 1;
    }
  }
}