This is where things are really getting interesting – out on the far margins, where risk, spontaneity and contempt for easy definition count for a lot more than chops, tunes and the is-it-or-isn't-it-alternative argument. These three records are rock mostly by association: There are guitars aplenty, and there is some serious riffing going on, especially on the Crimson disc. But on Millions Now Living Will Never Die, the Chicago group Tortoise draws from a wide range of deviance: the dark pulse and melodic abstraction of '70s German avant-rock; the hypnotonal minimalism of vintage Steve Reich and Terry Riley; the distended rhythms of ambient dance music; lush chamber jazz; Brian Eno's experiments with shades of silence. And that's just on the 21-minute opening track, "Djed." Tortoise rely on shadow and suggestion to upset convention, but their ethereal subversion is a pleasure.

Bardo Pond, from Philadelphia, play deep-fried space music, the kind of liquid-distortion erotica neatly summed up on Amanita by the song title "Tantric Porno." (Those of you who take a dimmer view of this kind of murk might suggest the track title "Wank.") The Pond's stylistic polestars on Amanita, their third album, are plain enough: the lysergic outbursts of very early Pink Floyd and Amon Düül II, and the ebb and flow of Sonic Youth's howling guitar harmonics. Yet the luxuriant texture and rubbery tension of Bardo Pond's milky corrosion can suck you in like quicksand.

King Crimson were working without a net back when Bardo Pond were mere tadpoles. The current double-trio incarnation has been well documented on record in the past two years, but Thrakattak – an hour of stage tapes from late '95 with founding guitarist Robert Fripp and the rest of the band in flat-out, free-improvisation mode – is a visceral treat, a document of amazing technical might and telepathic precision. Crimson don't just fuck around; they fuck you up with sustained invention like the harrowing double-guitar passages in "The Slaughter of the Innocents." In a word, brilliant. Here are two more: Buy it.

For information, write to Thrill Jockey, PO Box 476794, Chicago, IL 60647; Matador Records, 676 Broadway, New York, NY 10012; Discipline Global Mobile, c/o Possible Productions, 351 Magnolia Ave., Long Beach, CA 90802. (RS 750/751)

DAVID FRICKE