Halfway through the ICP Orchestra's Aan & Uit, the 10-piece ensemble surges into "Barbaric," a swanky Hoagy Carmichael number he recorded with the Mills Hotsy Totsy Gang in 1929, and suddenly you get a fix on the ICP and maybe the entire Dutch avant-garde. Try to imagine free jazz emerging from 1920s Chicago speakeasies and the Paul Whiteman Orchestra and you've got an idea of the mix-and-match. Misha Mengelberg, the pianist who wrote most of the originals and presumably arranged "Barbaric," delights in finding dark corners in what used to be called light music. "ICP" originally stood for Instant Composer's Pool, but that was back in the '60s; there are still moments of what probably only sounds like scratch improv, but anyone hoping for either straight-ahead blowing or madcap, devilishly complex orchestral passages doesn't have long to wait. Ab Baars's dark, mewling tenor is prominently featured, and Mary Oliver's violin adds purr. But the real treat is hearing Mengelberg and drummer Han Bennink coming together to practice their rhythmic and harmonic geometry. There are plenty of Monk-influenced pianists, even if few are as individualist as Mengelberg. But can you name another drummer?