This is Spinal Tap
(1984)

The disastrous tour takes a heavy toll on the band. Ian Faith angrily quits as manager, and Nigel Tufnel angrily quits as lead guitarist.

During the band's final, farewell performance in America, Nigel rejoins the band on stage, and the reunited Spinal Tap head out on a successful tour of Japan. (All except drummer Mick Shrimpton, who dies via spontaneous combustion during that farewell concert.)

Thanks John L!