Possible Clues:

• Mockumentary about "one of England's loudest bands"
• 1984 mockumentary about a fictional heavy metal band
• 1984 rockumentary film parody
• 1984 mock rockumentary
• Pianist has split pants in rock spoof
• 1984 mockumentary with a lot of ad-libbed dialogue
• 1984 rock mockumentary
• Film featuring the fictional album 'Smell the Glove'
• Classic 1984 film in which most of the dialogue was ad-libbed
• 1984 Rob Reiner rock music satire