Fans have flocked to a church in Germany to hear a chord change in a music which lasts for 639 years.

Axar.az reports that, it is the first chord change to As Slow As Possible in seven years.

The work by avant-garde composer, John Cage, is one of the world's longest and slowest pieces of music.

The piece began 19 years ago with a pause lasting nearly 18 months. The change of chord took place on the specially-built organ on which the composition is being performed.

The Saint Burchardi Church in the city of Halberstadt started playing the music in 2001 and the last note change took place in 2013.

The score is made up of eight pages of music, to be played at the piano or organ - very slowly.

But the wait for the next scheduled chord change will be quick in comparison - with 5 February 2022 slated as the date.

The piece will end in 2640.

Cage, who passed away in 1992 at the age of 79, wrote the piece in the 1980s.

The composer is arguably most famous for 4'33", which is simply made up of four minutes and 33 seconds of silence.