This is the longest piece I have ever composed.
Of course, that’s because I cheated with an absurdly long repeat. I used to think the legitimately longest composed piece was ASLSP by John Cage, despite the fact that Cage himself considered the piece to be anywhere between 20 to 70 minutes in duration, not 639 years, but it turns out I was wrong. At this time that honor goes to the 1000 year long Longplayer by Jem Finer, a non repeating work for Tibetan singing bells, a live stream of which can be heard here, at least at the time of this posting.