The Polovtsian Dances (or Ballet Music), started in 1867 is perhaps the best known selection from Alexander Borodin’s opera Prince Igor. They are often played as a stand-alone concert piece as one of the best known works in the classical repertoire. In the opera the dances are performed with chorus, but concert performances often omit the choral parts. The dances do not include the "Polovtsian March" which opens Act III (No. 18), but the overture, dances, and march from the opera have been performed together to form a suite from Prince Igor. In the opera Prince Igor the dances occur in Act II (in the original edition). He never finished his opera. It was completed by Rimsky-Korsakoff and his pupil Glazounoff, and three years after his death received its first performance.