Last weekend I stumbled around Manhattan trying to take in the bonanza of the annual Winter Jazzfest. The event has expanded from two days to six, but its heart remains a two-night marathon spanning Friday and Saturday. This year more than 150 first-rate groups performed downtown at more than a dozen venues. Winter Jazzfest takes place during the annual conference of the Association of Performing Arts Presenters, where curators and programmers talk shop and check out artists who want the organization’s members to book or hire them. This can make the Winter Jazzfest function something like a bazaar, where browsing is encouraged—sets are sometimes disrupted by crowds entering or exiting during the music. On the plus side, though, there are few other opportunities anywhere in the world to hear so many groups in such a short time.