As a drummer, you control those tracks. If you do not actually start or stop them; you at least must play along and remain in the right section at all times. To do this, you need to play along to a click track (metronome) which is in sync with the prerecorded tracks. You may play 32 bars before you here any samples but your job is to know exactly when that sample hits. Perfect tempo and song knowledge is key here.
Without going into too much detail on equipment and technique; I will leave you with this. Next time you here sounds that no one on stage is producing; chances are the drummer knows and may be controlling it.