I started listening to Composition 40F/23J. It is clearly very fine music, full of ideas etc. And these guys are obviously a team, and produce some long incandescent passages.
But there’s something about the timbre of the ensemble which I don’t like, all that music made by blowing through metal tubes - even though they make some unexpected noises. Maybe I’ll acclimatise to it. But there’s another thing which I really don’t like and I may not acclimatise. The structure is basically a lot of passages of people grandstanding one player after the other, like a concerto, like trad jazz. That’s a bit hard for me.
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Yes, I see your point about the timbre. That was actually the first Braxton recording I ever bought. I enjoyed a couple of the tunes, but found the disc overall a bit strident and sold it (at a decent price, the recording is well-regarded by fans).
In view of your feelings about explicitly "jazzy" material, you'll have to look carefully at the instrumental makeup of the ensembles. One of Braxton's most praised quartets had Marilyn Crispell (she's great, for example featured on some fine recordings with Barry Guy / LJCO*) on piano, Mark Dresser on bass and Gerry Hemingway on percussion. There's a Hatology twofer (also available as 2 single discs) with that group's swan song at Santa Cruz 1993. I have the recordings, think they're pretty good.
Lots of Braxton soloing, however, so YMMV.
I have no experience with Braxton's music for strictly "classical" instruments. Going to listen to as much of the Hildegard Kleeb recording as I can find on Youtube, as well at operatic selections on Bandcamp.
Composition No. 82 for four orchestras is also on the list, though I'm sceptical about the multi-orchestra aspect coming across on recording.
*Can't in good faith recommend LJCO to you, though. Many metal instruments and brassy timbres.