The organ composition is called “As Slow As Possible.” It’s currently being performed in a church in Germany.

The first chord proper whooshed through the pipes in February 2003, prompting complaints from neighbours that it was too noisy. In 2011, a way was found to reduce the air pressure. “We haven’t had any complaints since then,” says Neugebauer.

Of Halberstadt’s 40,000 residents, he calculates, about half don’t even know the concert is still going on. “The other half may not know what to make of it, but they appreciate it’s good publicity for the town.”

Some people who seek out St Burchardi church have travelled far and wide. They ask to be locked in the church on their own for hours at a time, or have been granted the wish to spend a night next to the humming organ. “I know people who thought the whole idea was a load of overintellectualised nonsense,” Lautenbach says. “And then they step into the church and they are absolutely enchanted.”

Ensuring “As Slow As Possible” manages to keep going for another 616 years remains a challenge, not least in financial terms. The project relies on donations alone, but all of the “sound plaques” inside the church – one for each year of the piece’s running time – have been sold. The latest fundraising scheme is a chance to book a seat for the end of the show on 4 September 2640 (tickets are transferable). —Guardian