U2 have made their current European tour a testing ground for new material. The best of the new live songs is "Mercy," cut during the sessions for 2004's How to Dismantle an Atomic Bomb but not on the album. The band has reworked "Mercy" for the stage, turning it into a big bear hug of a ballad that almost sounds like it could have gone on Joshua Tree. "You're going to kill me, and I want to die," Bono sings against the Edge's spacey arpeggios. "We were meant for each other." Other tracks that thrilled fans this summer include the intensely rocking "Return of the Stingray Guitar," the psychedelic "Glastonbury" and the starkly beautiful "Every Breaking Wave." The latter recalls "All I Want Is You," with Bono delivering dark poetry like "The waves know we're on the rocks/Drowning is no sin." U2 say they have four separate albums in the works; if so, this is a good start.

Photos: U2: The Rolling Stone Covers

“Oh Sherrie”

Steve Perry's girlfriend Sherrie Swafford was actually in the studio when Perry began writing this song--his lone Top Ten hit as a solo act--with two co-writers. The trio began at midnight one night with just "Oh, Sherrie!" and "hold on, hold on." Three hours later, they had a complete song. Swafford, however, had to wait until the next day to hear it. "Sherrie actually got tired and went to bed," Perry said. She also appeared in the video, but their relationship did not hold on for long.