Castor & Pollux is a dance piece that tells the story of Leda with the swan and the birth of the twins Castor and Pollux. Partch's score consists of two halves, one for each of the twins. The first three scenes of each half are written for two instruments and are played by two dancers. In the final scene Chorus of Birth from the Egg, all six musicians and six dancers act simultaneously: a dynamic superimposition of rhythm, melody and harmony.