Experimental doesn't begin to describe Glenn Branca. As one of the most ambitious, esoteric guitarists affiliated with the late '70s No Wave scene in New York, Branca pioneered the use of impossible, quasi-mystical tunings — a reinvention of classical structures by way of skull-crushing electric guitars. (Think Sonic Youth crossed with Mahler crossed with a barnstorming DC-9, and you're halfway there.) His appearance in St. Louis matches the composer with the Saint Louis Symphony Orchestra for the world premiere of Branca's Symphony No. 14, Frank Zappa's "G-Spot Tornado," Edgard Varése's "Arcana," and, finally, Symphony No. 13, "Hallucination City," a Branca composition performed by a 100-strong volunteer guitar army. Ears will bleed, minds will melt, the heavens will crack and angels will hail the satanic genius of superabundant microtonal cacophony — and that's just at sound check.