Songs often use syncopation, which is the accenting of unexpected beats. In general, the difference between disco, or any dance song, and a rock or popular song is that in dance music the bass drum hits four to the floor, at least once a beat (which in 4/4 time is 4 beats per measure).[citation needed] Disco is further characterized by a 16th note division of the quarter notes as shown in the second drum pattern below, after a typical rock drum pattern.