The piece
Cage wrote ASLSP for piano in 1985 and arranged it for organ in 1987. The score is eight pages. Its only tempo instruction is the title: as slow as possible. A piano performance lasts 20 to 70 minutes.
The performance
The foundation chose 639 years, the gap between the first documented permanent organ in Halberstadt Cathedral, around 1361, and the year 2000 first proposed as the start. Lack of money delayed the opening by a year, so the performance began on 5 September 2001 and the first sound came on 5 February 2003.
Every chord change happens on the 5th of a month. The changes for the first part of the score, which ends in 2072, were calculated by Christoph Bossert and Rainer O. Neugebauer.
The instrument
The organ was built for the performance. The bellows run continuously and sandbags hold the pedals down so the notes keep sounding. In 2008 two more pipes were added to the four already installed, and the tone became more complex.
The programme
| No. | Action | Notes | Date | Chord length |
|---|
The change log of the performance, as published by Wikipedia. "Sound" adds notes, "Release" removes them; the chord sounding at any moment is what remains. Rows with the same date belong to a single change. The schedule shown runs to December 2039; the first part of the score continues to 2072, and the closing chord is set for 5 September 2640.
This week: the 17th chord change
5 August 2026, Burchardi church, Halberstadt
14:00Doors open; the outdoor broadcast begins.
14:45The chord changes. Admission is free.
15:30The church's sound space opens to everyone.
A premium area with a direct view of the organ and the ceremony is reserved for a donation of €200 to the foundation. The church is closed on 4 August for organisational reasons. The supporting programme opens on 3 August with Something for Nothing, by Jeffrey Lependorf.
How it is paid for
The performance has had no state or institutional funding since it began. It is kept going by volunteers, by donations, and by 639 sponsorship plaques on the church walls, one for each year of the performance. A FINAL TICKET for the closing night, 5 September 2640, is on sale now.
The chord now sounding began before this page did.
If you were born after 5 September 2001, the concert has been playing for your whole life.
Sources: the John-Cage-Orgel-Kunst-Projekt Halberstadt (aslsp.org), Wikipedia's entry on ASLSP, and The Observer, 4 February 2024. Everything here is computed in your browser from your device's clock; nothing is sent or stored. Test hooks: ?at=2026-08-05T14:45+02:00 shows the page as it will read at the change; ?at=2026-08-06 shows it the day after.