Attributed to Wynton Marsalis in A Dirty Job by Christopher Moore:

Jazz was a zen art. Controlled spontaneity. Like sumi-e ink painting. Like haiku. Like archery. Jazz wasn’t something you planned. It was something you did. In jazz, every moment is a crisis and you bring all your skill to bear on that crisis. It’s all right there. No future. No past. Just that moment and how you deal with it. Art happens.