The God-drums are a sound track played over the speakers in the city of Lud. Everytime they are played the Pubes sacrifice one of their own in the belief that it will prevent the ghosts of Lud from destroying them.
In reality, the God-drums are a malfunction. The di-polar computers under Lud have lost most of their functionality, but can still play this track over the speakers. The God-drums are the drum track from the ZZ Top song, Velcro Fly.