A 639-year-long musical performance just changed chords for the first time in two years - and it's not set to finish until 2640: "It's a way of trying to slow down our hectic lives"

It's no secret that songs have been getting shorter for decades; since 1990, the average length of a song on the Billboard Hot 100 has gone from above four minutes to 3 minutes and 15 seconds. 

Not everyone is speeding things up, though. For over two decades, the longest piece of music ever written has been in performance in Germany, and this week, the piece just changed chords for the first time in two years. 

Yes, you read that right - this particular performance of the piece, John Cage's Organ²/ASLSP (As Slow as Possible), began in 2001 on Cage's 89th birthday and isn't scheduled to finish until 2640, with the total duration reaching 639 years. This latest chord change is only the 16th to occur in 22 years, and the next won't happen until 2026.

As Slow as Possible was written in 1985 by renowned experimental composer John Cage. Initially written for piano, it was reimagined as a piece for organ two years later. While the piece doesn't specify a tempo, the title's instruction to performers is clear: play the piece as slowly as you possibly can.

The avant-garde composition is being performed in the 11th-century Burchardi Church in Halberstadt, Germany, using an electromechanical organ built specifically for the performance. Sandbags hanging from the organ's pedals maintain the continuous notes, while air is blown into its pipes by an electronic fan. 

When the project was conceived, the designers weren't able to afford the construction of an organ capable of playing all of the notes in Cage's piece, which would have required 89 pipes. 

Instead, they designed an instrument with nine holes for pipes that can be swapped out when necessary; the most recent chord change required a new pipe be added to the organ so that a D can be added to the chord currently being played.

Hundreds of visitors travelled to Halberstadt to witness the sounding of the extra note, many of whom booked their tickets years in advance. The John Cage Organ Project, the organization behind the performance, is already selling tickets to the end of the show... 616 years in the future.