Organ²/ASLSP (As SLow aS Possible) is a musical piece by John Cage and the subject of one of the longest-lasting musical performances yet undertaken. It was originally written in 1987 for organ and is adapted from the earlier work ASLSP 1985; a typical performance of the piano version lasts 20 to 70 minutes. In 1985, Cage opted to omit the detail of exactly how slowly the piece should be played.
The performance of the organ version at St. Burchardi church in Halberstadt, Germany, began in 2001 and is scheduled to have a duration of 639 years, ending in 2640.
