There are two kinds of festivals within the six nights (and one day) of the Vision Festival. There's the festival for people who travel to get there and the festival of people who travel to play. Vision is the highest concentration of New York energy jazz in the world, a fact that year after year seems to eclipse its "world class" (if there's reason to use such a phrase) nature. It is at once a chance to hear within a tight schedule (this year sticking closer to advertised times than ever) the cream of NYC's hard improv: Sabir Matteen, Roy Campbell Jr., William Parker, Borah Bergman, Daniel Carter, Rob Brown, Steve Swell, Billy Bang, Henry Grimes and (for the last time as such) the David S. Ware Quartet. But their presence, and that of such perennial associates as Kidd Jordan, Hamid Drake, Bill Dixon and Joe Morris, shouldn't overshadow the sweet surprises each year brings.