int buzzer = 7;
int btn = 6;

void setup() {
  // put your setup code here, to run once:
pinMode(buzzer, OUTPUT);
pinMode(btn, INPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
if (digitalRead(btn)== HIGH){
  tone(buzzer, 400);
digitalWrite(buzzer, HIGH);
}
else {
  noTone(buzzer);
  digitalWrite(buzzer, LOW);
}
}