Gustav Mahler’s Tenth Symphony, his final composition, consists of sketches for five movements. The material as he left it is unperformable. Since his death, in 1911, many brave souls have attempted the impossible task of filling in what the master left unwritten. The first such performing edition had its premiere in 1964. Now Teodor Currentzis, a conductor of visionary inclinations, presents “various compositional perspectives in response to Mahler’s unfinished 10th Symphony,” including new music by Philippe Manoury, Mark Andre, and others. We’re also promised a performance of the Tenth itself. —Matthew Gurewitsch