The longest recorded song is "Longplayer", composed by Jem Finer, a British musician, and debuted on January 1, 2000. - Apparently.
Longplayer is an infinite piece of music that began playing at the same moment the year 2000 began. It is programmed to continue indefinitely, with its composition evolving over time according to a complex algorithm. The song has been running non-stop for over 22 years, with no repetition in its 2.5 million possible permutations.