A study on repetiton and the passing of something you never quite managed to lay your hands on, perhaps best exemplified by the fact that the repeated figures of this piece don't start where you think they really start. The timings are deliberately obscure. Something is passing before your eyes and you just cannot see it.
A threnody is defined as a song, hymn or poem of mourning composed or performed as a memorial to a dead person. At least that is the way Wikipedia phrases it this week. It may be a different definition next week. Sure, the tune here is mournful and plays on a cycle of four chords on a ground bass and it's all very minor key model and gloomy. As a closure to a particulary fertile period of music making it seemed apt.
This is also available on YouTube.