Wolfgang Sawallisch’s time directing the Philadelphia Orchestra is coming to an end. “The 79-year-old maestro, who restored the trademark Philadelphia string sound, performed Beethoven and Brahms with matchless authority, and premiered important new works by American composers, has long lived his public life in a businesslike, nonconfiding fashion. Though his charm and still-hearty handshake suggest he’s always glad to see you, there’s a sense that his availability has fairly strict limits, ones not to be challenged.”