What is the scheduled duration of John Cage's organ piece performance at St. Burchardi church?

John Cage's organ piece, known as "As Slow As Possible," was composed with the intent of being performed over an extraordinarily long duration. The performance at St. Burchardi church in Halberstadt, Germany, is set to last for 639 years, which began in 2001 and will conclude in 2640. This prolonged duration reflects Cage's exploration of time, sound, and silence, demonstrating his innovative approach to music that challenges traditional conventions. The choice of 639 years corresponds precisely to the unique structure of the piece, which emphasizes the gradual unfolding of sound and the experience of listening over an extended period.