Psychedelic music ranges from unbearably weightless (Gong's three "Radio Gnome Invisible" albums) to black-hole heavy (the Jimi Hendrix tune "Are You Experienced?"), and these two groups definitely have a bit of ballast. Since 1989 guitarist and singer Eric Arn, formerly of Crystalized Movements, has led the Primordial Undermind through myriad mutations in lineup and sound. On the band's first release, a 1992 seven-inch called Sferic Mandalas From the Ecclips'd Eye (Baby Huey), the title and cover art are more psychedelic than the music--a barrage of garage-punk riffs, barked lyrics, and concise, Television-like guitar solos. But on the Undermind's fourth and most recent album, last year's Beings of Game P-U (Camera Obscura), Arn plays mostly improvised and thoroughly psychedelic jams with violinist Travis Weller, drummer Jared Barron, and Charalambides guitarist Tom Carter, eschewing vocals entirely. Only Arn and Barron are traveling with the version of Primordial Undermind that will play here, though--a sextet with two drummers, two guitarists, a bassist, and someone playing a simple knobs-and-oscillators synthesizer called a Triwave Picogenerator. Guitarist Steven Wray Lobdell, leader of the Davis Redford Triad, kept his trap shut during his stints with German prog pioneers Faust and the Baseball Astrologer, and no one at all sings in this band. In fact, on the Triad's 1997 debut album, The Mystical Path of the Number Eighty Six (reissued this week by Holy Mountain in a new, beefed-up mix), it'd be pointless to even try: vocals would just get blown away by the squalls of feedback and fuzz that scud across the dark, roiling surfaces of pieces like "Solar Aquarius" and "Hymn of the Virgin Sun Queen." Bassist Matthew Freid and percussionist Jeffrey Helwig are holding down the other two corners of the Triad on this tour. They'll play first, followed by local space rockers Grimble Grumble; Primordial Undermind headlines. Wednesday, May 22, 9 PM, the Hideout, 1354 W. Wabansia; 773-227-4433.