In a small church in Halberstadt, Germany, an organ has been playing the same chord since 2003. The next chord change is scheduled for early 2026. The performance is As Slow as Possible by the American composer John Cage. It started in 2001 with a year of silence — because that is how the score begins — and it will finish, according to the performance plan, in 2640.

That is a 639-year performance.

Cage originally wrote the piece in 1985 for piano. The original performance ran twenty to seventy minutes, depending on interpretation. After Cage's death in 1992, an organist named Heinz-Klaus Metzger and a Cage Society in Germany posed a literal question: what is the actual slowest possible? An organ can sustain a note essentially indefinitely, as long as someone keeps the bellows running. So why not stretch the piece across centuries?

The site at the Burchardi Church in Halberstadt was chosen for symbolic reasons. The town had hosted what historians believe was the first known instrument with a modern twelve-tone keyboard, an organ built in 1361. The interval from 1361 to the year 2000 — when the project was conceived — is 639 years. So the piece itself was set to run for 639 years.

The custom-built organ uses sandbags placed on the pedals to hold notes. Volunteers replace bags during chord changes, which happen roughly once every year or two. Each chord change attracts hundreds, sometimes thousands of pilgrims. The next is on February 5th, 2026.

A nonprofit trust funds the organ, the bellows, and the staff. The performance must outlast wars, economic crises, and probably the languages spoken in the church today. It is a piece of music designed not to be heard by any one human being.