The world's longest performance of a piece of music began at midnight in a small German town - and will last a staggering 639 years.

The sole item on the programme is an organ composition by the revolutionary American composer John Cage (1912-1992), entitled Organ2/ASLSP.

It was originally a piece for piano lasting just 20 minutes and entitled ASLSP (As Slow As Possible), but the organisers of the concert decided to take the American composer John Cage quite literally.

The audience gathering at the former Buchardi monastery in Halberstadt will not hear the first chord for another year and a half.

Sound of bellows

All they will get is the mellow sound of the organ's bellows being inflated.

If that fails to take the audience's breath away, the organisers, the John Cage Project, have laid on a dance performance and two connected organ concerts conducted at a more sprightly pace to fill the gap.

The organisers say the lengthy performance is supposed to contrast with the hectic pace of change in the modern world.

Halberstadt is known for its famous organs, and the duration of the piece was chosen to reflect the building of the first of a series, 639 years ago.

If everything goes to plan, the audience could be allowed an interval for refreshments and a nip to the loo in about three centuries.

Allowing for a couple of curtain calls, they will probably spill out onto the streets looking for a taxi in the second half of the millennium.