A brief entry in the 1974 edition of the Guinness Book of World Records cites the Sleepytime Gorilla Museum as the “World’s Most Closed Public Institution” — one that operated openly for only 47 days of its 34-year existence. Shuttered up after crowds gathered in Manhattan’s meat-packing district for a “free salamander exhibit” (they were greeted instead with a staged fire and fake money being thrown from a warehouse window), the museum attracted anti-artists, anarchists and primitive musicians allegedly influenced by Italian futurist Lala Rolo. In a similarly costumed freak show, San Francisco’s Sleepytime Gorilla Museum holds Dadaist court at the Lion’s Lair Tuesday, January 22, juggling a public spectacle of self-destruction, tricky time signatures and improvised racket. Equal parts opera, prog wank and hard-slamming metal, the collective boasts some of the Bay Area’s most adventurous music-theory geeks: scary frontman Nils Frykdahl and instrument builder Dan Rathbun (both late of Idiot Flesh), co-vocalist Carla Kilstedt (violinist for Tin Hat Trio and Charming Hostess), drummer Frank Grau and industrial-waste percussionist Moe! Staiano. Touring in support of Grand Opening and Closing, the band’s text-heavy debut on Negativland’s Seeland label, SGM offers an unrelenting mix of noise and lullaby, confusion and fear. Banging and clanging on homemade gadgetry that would make Harry Partch drool, including the spring-nail guitar, pressure-cap marimba and slide-piano log, these Victorian-garbed curators unlock the zoo of their own mythical making with a tribute to chaos and black math. The past is no more real than the future.