Complex sentence: The 21 completed pieces include solos, duos, trios, a septet, and Stockhausen's last entirely electronic composition, "Cosmic Pulses", and they bear the work (opus) numbers 81--101.
Split into simpler sentences: The 21 completed pieces include solos, duos, trios, a septet, and Stockhausen's last entirely electronic composition, "Cosmic Pulses". The completed works bear the work (opus) numbers 81--101.