The rhythm is laid down by prominent, syncopated basslines (with heavy use of broken octaves, that is, octaves with the notes sounded one after the other) played on the bass guitar and by drummers using a drum kit, African/Latin percussion, and electronic drums such as Simmons and Roland drum modules.
Most disco songs have a steady four-on-the-floor beat, a quaver or semi-quaver hi-hat pattern with an open hi-hat on the off-beat, and a heavy, syncopated bass line.