Complex sentence: Slash worked with Guns N' Roses band mate, and drummer, Matt Sorum on the demos, before guitarist Gilby Clarke and Alice in Chains bassist Mike Inez joined them, jamming and recording most nights.
Split into simpler sentences: Slash worked with on the demos Guns N' Roses band mate and drummer Matt Sorum. They were later joined by guitarist Gilby Clarke and Alice in Chains bassist Mike Inez, jamming and recording most nights.