The challenge, and thrill, of Hector Berlioz's 1846 The Damnation of Faust—not quite an opera, not quite a symphony—is that you can do anything you like with it. Berlioz certainly wasn't concerned with convention in his evening-length work for orchestra, four solo singers, and two choruses; he even wrote a prologue to the score basically saying, "Yeah, I messed around with Goethe's version of the ancient legend to suit my own needs, and what of it?" The choruses represent, at various times, "peasants, gnomes and sylphs, soldiers and students, demons and the damned, and celestial spirits," which gives you some idea of the work's fantastical scope. Berlioz even invented his own "demonic" language for the chorus to sing ("O meri kariu! O mevixe!"). The Met staged Damnation cinematically a couple of seasons ago, surrounding the singers with projected animations; Monty Python's Terry Gilliam made his opera-directing debut last year in a British production that evoked Kristallnacht and Leni Riefenstahl; and when the Seattle Symphony last played it, in 1995, Gerard Schwarz filled the aisles with a candle-bearing children's choir as a grand finale. Hopefully SSO has something memorable cooked up for this weekend's concerts, which close Ludovic Morlot's first season as music director. Berlioz let his imagination run rampant in the score, and though the music on its own never fails to dazzle, there's no better opportunity to do something onstage other than present the same old platoon of tuxedos.