Bob rock is a guitarist turned producer who played bass for Metallica for few gigs. Check out his band, Rockhead. Not bad.

And what Richie has told about Bob Rock is actually pretty far away from "rock". He was almost anal with all the overdubs and things, he made the boys record everything over and over again until he thought it was just right. Richie later said that it wasn't too enjoyable experience, he prefers real playing instead of making record in little pieces. Said it didn't feel like he was really playing.

Ice