Earth and Venus have a nearly synchronized orbit. For every eight Earth years, Venus orbits almost exactly 13 times. The slight drift between them takes 239.8 years to rotate the resonance shape by 1/5 of the circle (which is 30x the 8-year cycle), then 1199 years to rotate one full round, which is 150x the 8- year cycle minus 1 year.
The piece includes a repeating mensuration canon. The lower part plays its 13 equal notes in the time taken for the higher part to play the first eight notes of the lower part. Meanwhile the bottom part plays a slower five equal-length note pattern. After five repeats, it has drifted slightly out of phase with the canon, at which time it takes a different five note pattern, which repeats five times, drifting further out of phase with the canon. A new 5 note pattern is taken up. After different five note patterns have been played, the bottom part comes back into phase with the canon. These three sequenced parts provide the structure for a free, hand-played voice.