premise: Songbook is an acoustic live album by American musician and Soundgarden vocalist Chris Cornell, released on November 21, 2011. The live album features songs recorded during Cornell's Songbook Tour, an acoustic solo tour which took place during March–May 2011 in the US, and is his first live album as a solo artist.
hypothesis: Chris Cornell was a guitarist.
reason: He is a vocalist but he's also a guitarist.