Steve Turre, Wednesday, September 13, at the Mount Vernon Country Club, is best known to television audiences for his stint as a trombonist in the Saturday Night Live band. But in jazz circles, he's revered for his collaborations with Rahsaan Roland Kirk, Dizzy Gillespie, Ralph Moore and Woody Shaw, and as a bandleader/trombonist with a fascination for jazz played on seashells. Turre began pursuing the latter in 1970, while a member of Kirk's band, and in the years since then, he's acquired shells from three continents. Today, Turre's shell orchestra, the Sanctified Shells, consists of five trombonists and a trumpeter who double on shells and six musicians who play shells only, plus three percussionists and a bassist. The result is an enthralling combination of modern jazz and sounds made using organic instruments (the forerunners of brass and wind instrumentation). In short, it's an incredible visual and auditory delight.