Swan Lake, Op. 20, is a ballet composed by Pyotr Ilyich Tchaikovsky in 1875–1876. The scenario, initially in four acts, was fashioned from Russian folk tales and tells the story of Odette, a princess turned into a swan by an evil sorcerer's curse. The choreographer of the original production was Julius Reisinger. The ballet was premiered by the Bolshoi Ballet on 4 March [O.S. 20 February] 1877 at the Bolshoi Theatre in Moscow. Although it is presented in many different versions, most ballet companies base their stagings both choreographically and musically on the 1895 revival of Marius Petipa and Lev Ivanov, first staged for the Imperial Ballet on 15 January 1895, at the Mariinsky Theatre in St. Petersburg. For this revival, Tchaikovsky's score was revised by the St. Petersburg Imperial Theatre's chief conductor and composer Riccardo Drigo.