The selected audience at the medieval church of St. Burchardi in the east German town of Halberstadt were listening very attentively on Saturday, because the chord change on the organ they were about to hear was the first in almost seven years.
The event was a big deal to fans of the John Cage Organ Project.
The US musician, who died in 1992, was always laid back, but he surpassed himself with this composition called "Organ As Slow As Possible.
The first note was played in 2001 and the piece is due to finish in 2640.
The chord change was achieved by adding two additional pipes to the organ, on this occasion by soprano singer Johanna Vargas and organist Julian Lembke.
The next chord change is planned for February 5, 2022.
The organisers of the event said the performance is "one of the slowest realisations of an organ musical piece."
Given its length of 639 years, that's surely one of the greatest ever understatements.
Chord changes usually draw several thousand visitors to Halberstadt, but because of the coronavirus pandemic, the number of guests allowed into the church was limited this year.