Joe Satriani is one of the highest rated guitarist in the world. He played on five songs on the 'Hey Stoopid' album, including the duel solo on 'Feed My Frankenstein' with Steve Vai, and has an acclaimed solo career, releasing a string of highly rated instrumental guitar albums. He even played briefly with Deep Purple, standing in for Richie Blackmore when he walked out halfway through a tour. Reputably Joe was a big Cooper fan in his youth. Joe is also the guy who taught Steve Vai how to play. Nowadays he continues releasing acclaimed solo albums, as well as playing in 'supergroup' Chickenfoot with Sammy Hagar.
Joe has only played live with Alice once when he made a guest appearance on July 14th 1991 in Mountain View, CA show to play on 'Hey Stoopid'.
For more info check out satriani.com.