“Most modern productions of Swan Lake are derived from the 1895 staging at the Mariinsky Theater in St. Petersburg choreographed by Marius Petipa and Lev Ivanov, which had its premiere after Tchaikovsky’s death and for which Tchaikovsky’s score was drastically reordered and rearranged by Riccardo Drigo. The original 1877 Bolshoi Swan Lake … has been more of a cipher to posterity.” Until now.