Movies You Haven't Seen But Should: Phantom of the Paradise

From Wikipedia:

The story follows a music composer and singer named Winslow Leach (played by William Finley). Winslow's pop cantata "Faust" is stolen by Satanic record producer, Swan (played by Paul Williams). Winslow tries to get it back, and along the way falls for Phoenix, an aspiring singer (played by Jessica Harper). Swan orders his minions to frame Winslow for drug dealing.

In prison, after his teeth are removed and replaced with metal ones, Winslow goes berserk, escapes and tries to destroy Swan's record factory. His face is mutilated and vocal chords crushed in a record press accident. Winslow sneaks into Swan's concert hall and residence, the Paradise, and wears an owl-like mask and black leather costume so he can terrorize Swan's musicians.

Swan confronts Winslow, and offers the composer the chance to have his music produced and the return of his voice, in exchange for signing a contract in blood. Winslow agrees, on the condition that Phoenix is the lead singer.

Swan breaks the deal, seduces Phoenix, and puts a gay male prima donna named Beef (Gerrit Graham) in the lead of Winslow's "Faust". Winslow kills Beef, then learns that Swan made a Pact with the Devil years ago: Swan will live forever, with a youthful appearance, unless the videotaped recording of his contract is destroyed. Winslow's contract with Swan, in turn, says that that Winslow can't die until Swan himself has died.

Winslow Leach: "All art…"
[Swan has moved to the other side of the Phantom]
Winslow Leach: "All articles which have been excluded shall be deemed included." What does that mean?
Swan: That's a clause to protect you, Winslow.

And here it is, of course, on the IMDB