This is Spinal Tap (1982)

The first of the of the Guest/Shearer school of mockumentary’s seems the most subtle, you can buy Spinal Tap as a rock n’ roll band in a way you can’t buy The Folksman as folk musicians. Numerous cameo’s abound and the arc of the American tour seems, again, comicly plausible when compared to other rockumentary’s. Everything subsequent in the genera was really derived from this.