petipa gave tchaikovsky very special directions about tempi, meter, and other musical matters. he even specified the length of particular pieces in exact numbers of bars. he asked for a waltz in act 1, a mazurka in act 2, and a polonaise in act 3. the ballet is tied together (and its drama and suspense heightened) through the repeated use of the two musical themes representing good and evil, personified by the lilac fairy and carabosse respectively. petipa's specifications stimulated tchaikovsky's imagination, rather than hindered it as one might expect.