The PRISM Quartet performs tonight at Art After 5 at the Philadelphia Museum of Art, 26th Street and the Benjamin Franklin Parkway, starting at 5:45 p.m. BY DAVE ALLEN The saxophone, that iconic American instrument, is perhaps more freighted with artistic significance here in Philadelphia, where John Coltrane spent formative years and where other formidable, if less iconic, reedmen have launched their careers. In the Germantown section of the city, not all that far from where Sun Ra’s legendary Arkestra set up shop and where Arkestra saxophonist Marshall Allen still lives and sometimes assembles the group, another musical summit — […]