In his last Richmond appearance in April 2005, bassist William Parker closed with a beautiful, extended solo. The playing was both lyrical and angular, evoking and illuminating a vast, solid and shadowed sonic space. For more than 35 years Parker has been at the heart of the high-risk sonic alchemy of the New York Downtown free jazz movement, both as a leader (his latest CD, “Essence of Ellington,” was released Sept. 11) and as the muscular pulse for cutting-edge greats, notably Cecil Taylor. As before, his appearance is courtesy of Richmond’s liaison to the best of the avant-garde: flamenco guitarist, bouzoukist and psychiatrist Ayman Fanous. Expect an adventure. “[Music] exists as a river of sound,” Parker says. “We throw a line into it; train ourselves to ride the wave, to know what to do when it comes through us. You don’t have to worry about creating. It informs you what to do.” William Parker and Ayman Fanous perform at St. John’s United Church of Christ on Friday, Oct. 5, at 7:30 p.m. $10-$15.