Deep Purple's definitive Mark II lineup reunited for 1984's Perfect Strangers. It is one of the better examples of a reunion album, although the band's uneasy camaraderie only lasted a few more years. "Knocking at Your Back Door" opens the album with a roar. Ian Gillan's lyrics don't make much sense, but Ritchie Blackmore's guitar riffs and Ian Paice's thunderous drumming carry this song as well as the rest of the album. The robotic rhythm of the title cut relies on Jon Lord's organ work. The 1999 remastered reissue features the bonus track "Son of Alerik." This fascinating, mid-tempo, ten-minute instrumental was the B-side of the "Perfect Strangers" 12" single in the U.K.