Fritzing

Piezo buzzer with an external reset button.

It is very simple: get a passive buzzer and a pushbutton. Connect both the pushbuton and the buzzer to ground - use two different ground pins on your board or connect both to the negative rail on a breadboard and ground that rail.
Next, connect the signal wire of the buzzer to a digitial pin. Finally, connect the pushbutton to the RST (reset) pin.

Load your passive buzzer program without any additonal code, and when you want the buzzer to play its melody again, simply press the pushbutton, and Bob's your uncle (let's not talk about the aunt - she's nuts.)