There is, it's safe to say, a lot going on with The Phantom of the Paradise. It's a collaboration between Brian De Palma, who as a director had just recently started going in the thriller direction he's best known for, and Paul Williams, who is best remembered for writing songs for Muppets and Karen Carpenter. Williams wrote all the songs for the movie, a musical/horror adaptation of Phantom of the Opera, which hadn't yet gotten the Andrew Lloyd Webber treatment. Williams wrote all the songs and also plays the chief villain, an evil reflection of Phil Spector. (The real Spector's murder conviction was quite a ways in the future.)
Things are primed for weirdness and De Palma delivers. The film starts with a voice-over from Rod Serling itself, leading into a doo-wop extravaganza that plays like if Sha Na Na were more death-obsessed. This is an introduction into the world of Swan (Williams), which is even more sordid than you might guess. At this point the antihero/secondary villain, Winslow Leach, is just a songwriter, a very naive songwriter who hands over originals of his work for Swan to critique, and three guesses how that works out. Before his lengthy but quick list of misfortunes and disfigurements, Leach looks like a wimpier Warren Zevon. He's played by frequent De Palma collaborator William Finley, who manages to keep much of his dopey innocence after the character has become a monster and a killer.
Are there flaws in the movie? Oh yes, yes indeedy. For one thing Leach's grand work is a rock opera about the Faust legend, but he doesn't balk at signing a contract in blood. And Swan's scheme unravels at the end due to what seems just a random discovery.
Still, there's fun to be had. De Palma has probably directed better movies, but this one has a go for broke spunk and absolute indifference to realism that keep it lively. He's never seemed to have more fun as a director.