I was walking back from watching the dance roller skaters in the park late one afternoon, when I heard drumming in the distance. Turning onto the walk to the Bandshell, I saw a huge crowd of bouncing onlookers clustered around more than a dozen men and women with all different kinds of drums, pounding out elaborate rhythms, while ecstatic dancers whirled and stomped in time. I had discovered the Central Park Drum Circle, a loosely knit group of passionate percussionists who jam on the weekends from April though October.