"Public Enemy was playing shows when we started," Rachel's leader Jason Noble said by way of introducing his chamber-rock ensemble Sunday night during a standing-room-only concert at the Cactus Cafe.

Man, has it really been that long? (That hip-hop group hasn't been a public force in years.)  The Louisville collective of rock musicians and string players dates back to 1991, but didn't release an album until 1995, when players in Noble's groundbreaking rock band Rodan went its separate ways. Many of these artists, as well as filmmaker Greg King (whose movies played in the background while Rachel's performed) worked with Rodan, and one gets the impression that this group is nothing more or less than a long-standing community of friends and neighbors that happens to make often-riveting, hard-to-classify modern music.

New York "chamber-core" (their tongue-in-cheek term) string quartet Invert opened the show with a nuanced set of dissonant themes and striking moments. Known for bringing rock dynamics to the centuries-old format, Invert alternated between its own compositions and discreetly chosen covers. A passage from Umebayashi Shigeru's score to "In the Mood For Love" was the prettiest moment, while their own piece "The March" was the most dramatic, a spectral theme and military-sounding base resolving into thunderous overtones.

Invert joined Rachel's for part of the latter band's set, which Noble said meant this tour was the first time the group had enough string players to perform some of their more detailed compositions, such as "Warm Body" and "Moscow/Clusters" - at one point, nine musicians were packed onto and in front of the tiny Cactus stage.

With King's films of silent cityscapes as the background, the core band quintet traded off instruments (various pieces included viola, laptop, drums, vibes piano and organ, cello, guitar and electric bass) for rockish pieces that had yet to be recorded ("F# Haze") and more dramatic themes (the deeply melancholy "And Keep Smiling," the warm, acoustic "Frenching"). Here's to 15 more years of the world's coolest chamber music.

Joe Gross