by Daniel Hathaway
At the end of a long concert season, the final performance in a series may be a happy or a bittersweet moment. For the Mosa String Quartet — violinists James Thompson and Brian Allen, violist Christine Wu, and cellist Anna Hurt — the last Arts Renaissance Tremont concert on Sunday, May 7 at Pilgrim Church was just about the last appearance the group would make as a quartet, for Wu and Allen are off to graduate studies at Juilliard and the University of Michigan, respectively.