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In St. Burchardi church in Halberstadt, Germany, the longest concert in history is playing right now. It began on 5 September 2001 and is scheduled to end in the year 2640 — a running time of 639 years.
The piece is John Cage's Organ²/ASLSP, whose score simply says 'as slow as possible'. A group of musicians and philosophers took the instruction literally and built an organ that never stops sounding, with small sandbags holding down the keys. Why 639 years? Because in 1361, exactly 639 years before the millennium, Halberstadt unveiled one of the world's first great organs.
Each chord change is an event: people fly in from all over the world to witness the moment the piece moves forward by a single note. The first seventeen months, by the way, were pure silence. Cage would have approved.