This is Spinal Tap (1984)

Factual error: In the scene where Derek Smalls is having trouble with the airport security the gate only beeps when he walks 'in'. The gate would beep no matter what way he walked through it. (00:41:00)

Nigel: The numbers all go to eleven. Look, right across the board, eleven, eleven, eleven and...
Martin: Oh, I see. And most amps go up to ten?
Nigel: Exactly.
Martin: Does that mean it's louder? Is it any louder?
Nigel: Well, it's one louder, isn't it? It's not ten. You see, most blokes, you know, will be playing at ten. You're on ten here, all the way up, all the way up, all the way up, you're on ten on your guitar. Where can you go from there? Where?
Martin: I don't know.
Nigel: Nowhere. Exactly. What we do is, if we need that extra push over the cliff, you know what we do?
Martin: Put it up to eleven.
Nigel: Elevn. Exactly. One louder.
Martin: Why don't you just make ten louder and make ten be the top number and make that a little louder?
[Pause.]
Nigel: These go to eleven.

Trivia: The band's name was originally going to be spelled "Spynal Tap," but it was changed because the band members wanted to fit in with the trend of misspelled band names. Harry Shearer later commented that "we later learned we spelled it right by mistake."

Question: Did any of the actors know how to play their instruments? Because sometimes Harry Shearer seems to know what he's doing on the bass, particularly during 'Big Bottom' but the two leads sometimes look as though they're playing air guitar.