Sufjan Stevens is no stranger to ambitious numerical concepts-- his 50-state strategy, like Howard Dean's, has generated no small amount of disbelief-- but the Brooklyn-based singer/songwriter has tended to keep even his epic songs to around the 7-minute mark. Then there was last year's half-hour BQE project. Stevens' new cover of Asthmatic Kitty signees Castanets' dark-hued Cathedral duet "You Are the Blood", recorded for the Dark Was the Night compilation, clocks in around 10 minutes, and it's an impressive encapsulation of his past musical directions as well as those that could be still to come. (An edited version is on the Dark Was the Night MySpace today).With the rhythmic complexity and noisy IDM experimentation of Radiohead's early-2000s work, "You Are the Blood" glides seamlessly between the electronics of Stevens' Enjoy Your Rabbit material and the grand symphonics that brought him to his widest audience yet with Illinois. Furiously rocking sections give way to intricately melancholic piano passages. Woodwinds whirl and feedback wails atop crunching digital beats, right before tumultuous horn fanfares fit for the soundtrack to some old violent movie that everybody takes too seriously. It's refined and cacophonous at once, working as much within the classical and jazz traditions as folk and/or rock-- Gerswhin meets Yorke, maybe? Then there's the song's portentous central metaphor.Stream:> Sufjan Stevens: "You Are the Blood" (Castanets cover)[from Dark Was the Night; due 02/17/09 via Red Hot]