Don't be fooled by the guest appearance of John Medeski, keyboardist from groove gurus Medeski, Martin & Wood.Altitudeisn't a good-time funk-and-shimmy jam-band record but a CD of out-jazz explorations that's like a sci-fi film score transmuted through Phish channeling Sun Ra. Well, OK--I guess Phish actually used todoall that on occasion, but this is with musicians who've spent most of their careers dancing on the knife edge.Altitudeis the third of Charlie Hunter and Bobby Previte'sGroundtrutherrecordings. The first two,LatitudeandLongitude, featured saxophonist Greg Osby and DJ Logic, respectively.  But this double CD blows the roof off their sonic explorations. Which doesn't mean there isn't a lot of fun and fury. It's just not always easy to grab onto, even when they toss out life rings of chunky rhythm matched to melodic riffing. Disc 1,Above Sea Level, is an electric storm. Besides his customary Hammond organ, Medeski plays vintage keyboards from the Moog to the mellotron, becoming a colorist dropping in space age sound effects.  Charlie Hunter jettisons his R&B; and jazz background in favor of early Sonny Sharrock shards of electro-distortion that often barely sound like the seven-string guitar he plays, let alone a regular guitar.  Bobby Previte plays electronic drums, often creating sound effects but also dropping in a funky groove like "Seoul Tower." But just as often, he's tossing garbage cans down the hill. Disc 2,Below Sea Level, is a pure free-form abstraction that suggests a meeting ground between Karlheinz Stockhausen and Keith Jarrett. Entirely acoustic, it manages to be both freer and more organic thanAbove. Hunter calculates angles between classical and prepared guitar while Medeski wanders around inside his piano and Previte plays with pots and pans in the kitchen. Yet there's an intuitive spirit here that culminates in the poetic rumination of "Mariana Trench." Groundtruther dare to step to the edge of the deepest abyss and the highest mountain. Sometimes they fly, and sometimes they fall.--John DilibertoMore from Charlie Hunter, Bobby Previte, and John MedeskiMisticoCopperopolisSongs from the Analog PlaygroundBing, Bing, Bing!The Coalition of the WillingThe 23 Constellations of Joan MiróMagoCombusticationFriday Afternoon in the Universe