The longest concert will last 639 years. The piece is called Organ²/ASLSP (As SLow aS Possible), written by John Cage in 1987, and there are no time limits on the work other than the instruction to play it “as slow as possible.” It is being performed by a specially built automated organ at the former St. Burchard Church in Halberstadt, German. The piece began on the composer’s birthday in 2001, and will last until 2640.
The Halberstadt performance is an art project that asks how slow “as slow as possible” can be, when that is the only instruction and no tempo is suggested. The length of 639 years was chosen because the start date was 639 years after the first organ was built. The performance began in 2001 with a 17 month pause. The first note was played in 2003. Months and sometimes years pass between note changes. The last note change was in 2013, and the next one is scheduled for 2020.
The score is only 8 pages. A typical performance of Organ²/ASLSP lasts 20-70 minutes, though it has also been performed at events for 12-24 hours.