Open Friends finds Coral Springs-based drummer Abbey Rader performing extremely challenging duets of improvised music with saxophonist Noah Brandmark. A serious Zen practitioner, Rader thunders and roils but with tremendous restraint; his sense of dynamics and rigorous control make him an outstanding and colorful accompanist with sticks, brushes, cymbals and chimes. Brandmark, whom saxophonist Dave Liebman refers to as “the white Sonny Rollins,” blows alternately fanged and meditative tenor sax and even foghornlike bass clarinet on one time. Although Open Friends was recorded in 1997, it was released just last year, and Rader and Brandmark have played a couple of sparsely attended gigs in support of it.