const int buzzerPin = 8;
const int buttonPin = 2;
volatile byte state = LOW;

void setup() {
  Serial.begin(9600);
  pinMode(buzzerPin, OUTPUT);
  pinMode(buttonPin, INPUT);
  attachInterrupt(digitalPinToInterrupt(buttonPin), tocar, CHANGE);
}

void loop() {
 Serial.print(state);
}

void tocar() {
  tone(buzzerPin, 440, 500);
  state = !state;
}