Of course, this isn't the first cyclical work RB has written, even if it is the longest. (cf Negatives and Opening of the Mouth.)
CONSTRUCTION is rather different from some of the other cycles so far mentioned - including those by Dillon and Ferneyhough. The longer work isn't only made up of a chain of smaller pieces, one after the other – those smaller pieces are also often laid over one another and heard simultaneously. Sometimes three or four at a time. In Opening of the Mouth some of those smaller works have also chopped up and redistributed. (The same may be true of parts of CONSTRUCTION, I don't know.) It's not a question of A + B + C etc. It's more like planets within a solar system or human beings within a society.
If you hear enough of Barrett's music, you can start to pick out the different pieces from the overall texture. Particularly the ones that you might already know. Hearing all these different, self-contained entities orbit around one another, both unified and separate, is one of the joys of the heliocentric movement, for example, and the source of a lot of its expressive energy.
And it can be equally revelatory to hear some of the smaller units on their own if you first knew them from their place within the larger work. I've had this experience with the flute and percussion duo Inward, which comes from Opening of the Mouth.