Side projects have historically offered artists an outlet to exorcise self-indulgent demons, resulting in tossed-off experimentations of fleeting interest. Thankfully, this scenario does not apply to Jonny Greenwood’s Bodysong. Too often, band members take off for the weekend, unload a vanity project to tape, and return with their deepest eccentricities expunged. (John & Yoko’s Unfinished Music, No.1: Two Virgins and Pat Metheny’s Zero Tolerance For Silence immediately come to mind as extreme examples of inaccessible pretension.) The art of the soundtrack has been especially problematic to the rock musician, for such a task is often better in concept than practice. Recent results have varied from dazzling (Badly Drawn Boy’s About a Boy, which was not a “proper” sophomore record, but sure felt like one) to half-baked (Neil Young’s Dead Man) to just plain embarrassing (Jeff Tweedy’s Chelsea Walls and most of Prince’s Batman).

Admittedly, Jonny Greenwood’s instrumental soundtrack to the film Bodysong is a beast of a slightly different breed. Created as a vital aspect of the film’s documentary style, Greenwood’s songs are intended as much more than incidental background music. Its collage of home video, newsreels, and cinema footage was edited to seamlessly incorporate the score and tell an abstract story of the span of human life. In his day job with Radiohead, Greenwood has emerged as the band’s most progressive member. He first stuck out as the guy robotically attacking his guitar in the “Creep” video, but has become increasingly obsessed with electronics, dissonance, and making instruments sound unidentifiable.

From its opening slaps and searing distorted screeches, Bodysong is violently coaxed into existence. Greenwood takes full advantage of his resources to craft track after track of invention: electronics swirl around an effected autoharp in “Moon Mall”; indeterminate layers of tribal percussion are thrown intentionally askew in “Convergence”; strings flutter like cicadas in “Moon Trills” and moan with pregnant sustain in “Iron Swallow”; a jazz combo freaks out in “Splitter”‘s heavily reverbed environment. He enjoys allowing the instruments to fly out of control, compete for existence, and then gradually bring them back to a coherent whole.

Listening to Bodysong, you realize just how essential Greenwood is to Radiohead’s chain of creativity. The songs feel like ghost echoes of tracks from the band’s catalog, and often you expect to hear Thom Yorke’s voice float in amid the organized chaos. The piano chords in “Moon Trills” suggest a minimalist interpretation of “Pyramid Song”; the backwards record loop in “Trench” is not unlike the rhythms of “Like Spinning Plates”; and the melodies plucked on banjo and acoustic guitars in “24 Hour Charleston” could be the genesis for “Go to Sleep”.

While this will all obviously appeal to Radiohead completists and fanatics, most casual listeners may ultimately find Greenwood’s experimental trip inessential or too difficult. Which is a shame, really, because with this soundtrack he has free reign to further explore creative tendencies that are actually interesting to hear. Bodysong boasts an abundance of forward-looking ideas and possibilities, a conversation between melody and cacophony that can provoke with finesse. Not only a worthy side project from one of the most popular groups in the world today, but a valuable addition to the petite canon of successful rock soundtracks that lives and breathes on its merits alone.