The entire point of this song is that it just never stops descending. Yet somehow the end is no lower than the beginning.
The chord progression is constantly descending and eventually becomes a kind of Shepard tone (sonic barber's pole): Em7 - Ebmaj7 - Dm7 - Dbmaj7 - Cm7 - etc, without ever resolving. The bassline is a more standard Shepard tone: a descending chromatic scale.
Mostly an experiment/proof of concept, haven't really worked too much with this but I might as well publish it.