Complex sentence: Mr. Stam is also quite sure that "Diary" served as a rough template for Spinal Tap's ill-fated 1984 tour but, unlike Tap, Mott was a real band on the way up.
Split into simpler sentences: Mr. Stam is also quite sure that "Diary" served as a rough template for Spinal Tap's ill-fated 1984 tour. But, unlike Tap, Mott was a real band on the way up.