“Dark Star” is a sort of loose, free-form jam that plays a pivotal role at Grateful Dead shows, and it’s been anywhere between five and 55 minutes in length. Toronto-based sound chemist John Oswald is known for his editing style of “plunderphonics,” whereby he builds a dense collage of pre-existing recorded material to create jaw-dropping murals (for a definitive taste, find his pop-blitzkrieg import album Plexure). In the late ’90s, Grateful Dead bassist Phil Lesh took some Oswald records to the rest of his band which, for one reason or another, had a match of aesthetics. It was decided that Oswald would be given free reign over 25 years of live “Dark Star” concert footage to create a definitive version of the piece for compact disc — which quickly became two compact discs. As with the typical performances of the song, this CD simmers to life quite passively. It’s as if the musicians (and Oswald) are all quietly throwing phrases around, waiting for something to stick. Patient listeners are rewarded around 40 minutes into the first disc, as more discernible themes start rearing their heads. “Fault Forces” takes a visceral stand with its overlapping train wrecks of fuzzy guitar burnouts, which give way to syncopated Weather Report rhythms and stoned Santana riffs. On the heels of this comes “The Phil Zone,” a strange little showcase for Lesh where the bass guitar buzzes and growls with feedback. The oddities continue with “La Estrella Oscura,” staggering about like a hippie flamenco dancer. Disc A (aka “Transitive Axis”) closes with “Recedes (While We Can),” a lean, straight-ahead groove that washes out into a cavernous void. In and of themselves these passages may not seem like anything special, but the comparative increase in structure is certainly appreciated. Disc two, or “Mirror Ashes,” continues shapeshifting between Woodstock blurriness and more cohesive moments, but it all fades away into murky, faceless, rumbling ambience at around the 15-minute mark, with “Cease Tone Beam,” a piece that drifts out of the atmosphere and straight into Kubrick’s monolith “beyond the infinite” (this would be an especially bad time for the drugs to be peaking). The familiar sounds do return in time, rising to a multi-layered drum cluster overdub at the start of “Dark Matter Problem,” a sort-of finale-flavored version of the rock noodlings that have sprouted intermittently for the past hour and a half. Along with extensive editorial commentary by ethnomusicologist Rob Bowman, there are detailed wave-file charts in the liner notes that itemize and time-stamp all the concert footage excavated for each passage. This is both a much-needed piece of the puzzle and a fascinating read. This double disc is a masterwork that belies all the effort that went into it. Due to the nebulous and organic raw material (and Oswald’s delicacy with it), Grayfolded rarely shows its cut-and-paste seams. This may actually disappoint some eager plunderphonic fans by how smoothly it flows. Conversely, some Grateful Dead fans may clutch their hearts in reverence, as if the band simply played a straight hour-and-45-minute song. The casual listener without the enlightenment of liner notes may dismiss it as meandering, and scholarly audiophiles may identify the quirks and technical magic the further along one gets. Ultimately, every opinion has some validity. Whether you’re a Grateful Dead fan or an Oswald fan, you will likely have your loyalty tested, since it’s such an epic and unique recording for both. It may be a bit much to call this a “controversial” album, but it does call attention to the study of music as much as the performance of it. – Glenn Swan