I could not resist a feature film about conjoined twins who are pressed into forming a Seventies rock band. And when I agreed to see it, I didn't yet know that Brothers of the Head was directed by the guys who made Lost in La Mancha, Keith Fulton and Louis Pepe, and was adapted from a Brian Aldiss novel by Tony Grisoni, who co-scripted Tideland, Fear and Loathing in Las Vegas, and the unfinished Don Quixote movie with Terry Gilliam. It sounded overall like my kind of movie, and I was not disappointed.

Brothers of the Head is a documentary-style narrative (the term "mockumentary" doesn't fit this movie) about Tom and Barry Howe, conjoined twins who were raised by a father and older sister on a remote coastal area of Britain. In their late teens, they are discovered by a music-industry impresario, who practically buys the boys from their father to front a rock band. He isolates them in a huge Oxfordshire mansion with other musicians and eventually they transform into sullen, angry, brutally attractive rockers. The impresario obviously had something genteel and clean-cut in mind, but the twins' music is edgy and raw, early punk rock. Luke and Harry Treadaway are amazing as the conjoined twin rockers. They don't say much, and in the beginning of the movie they tend to glare a lot. Barry quickly becomes the edgier one, smouldering with anger and hatred and jealousy, while Tom tries to make as normal a life as possible with his music and a girlfriend. One of the best moments of the movie has to do with a song Tom writes for his girlfriend, a sweet little love song that Barry wonderfully transforms into part of their punk-rock repertoire. Their odd, unique relationship is fascinating.

Brothers of the Head has more outright laughs in the beginning, when the setup seems like a joke and we don't know much about the twins. Ken Russell has a small role as himself, showing clips from an unfinished film of his about the Howe brothers. As the movie progresses and we learn more about the brothers, the tone grows much darker and more twisted, and the comedy fades into drama and suspense.

Fulton and Pepe manage to make this feature look like a real documentary; after the movie, they explained that they'd worked with the cinematographer to shoot scenes as if they were documentary interviews. Some sequences rely heavily on stills and audio recordings, which also adds realism. (At least one person in the audience seemed to think this was an actual documentary, but they may have been more gullible than the average moviegoer.) The band plays all their own music in this movie; no lip-synching or faking, which adds to the authentic feel of the film.

I was surprised by the light turnout for Brothers of the Head, but perhaps the bizarre premise made people feel hesitant about watching it. The film has another showing at SXSW on Thursday, and IFC appears to have distribution rights, so this movie isn't going to vanish into the night. Its edgy humor and oddly compelling lead characters make it well worth seeing, if you get the chance.