Cage originally conceived "ASLSP" in 1985 as a
20-minute work for piano, subsequently transcribing it for organ in
But organisers of the John Cage Organ Project
decided to take the composer at his word and stretch out the performance for
639 years, using Cage's transcription for organ.
The enormous running time was chosen to
commemorate the creation of Halberstadt's historic Blockwerk organ in 1361
-- 639 years before the current project