"he led the mazurka"

The mazurka is a lively Polish dance with three beats to a bar, where the accent falls on the second or third beat. It was popular in Russia, where composers such as Tchaikovsky, Glinka, Scriabin and Borodin all used the form. Tolstoy mentions the mazurka in Anna Karenina as well as here, and Turgenev uses it in a scene in Fathers and Sons.