Time Keeping... hehehe pano ba ito ieexplain hay.. sa aking view lang bro ah.. chempo, tyempo, whatever you want to call it.. may nabasa akong article dati.. basically the role of a drummer is "comping" parang mag-accompany.. to give beat to other music instruments.. pero xmpre, not just plainly accompanying the ensemble.. along with that accompaniment (tama ba spelling? nabobobo na ako eh.. T.T), it is the drummer's obligation to keep the time.. maintaining the chempo in a CONSTANT manner... hindi bumibilis, hindi bumabagal, but CONSTANT..
psensya na po sa paliwanag.. i hope this helps a little..
cheers!