According to Ozier Muhammad of the New York Times' photo blog Lens, it's Morningside Park (trombonist Chris Washburne), a semi-soundproof booth in a Chelsea studio (bari saxophonist Claire Daly) and a 3,000-square-foot loft in the Bowery (pianist Joel Forrester) — among other places. Check out Muhammad's full "Sounds From Uncommon Spaces" series, featuring several musicians of different stripes. We're promised 12 columns when all is said and done, so there's more to come. [Lens: Ozier Muhammad archive]
Thinking further: if you're a jazz musician, where do you manage to practice?