Well, when I write "more accessible" that indeed means the rest is harder to get into. No shame, though. It's a bit of an acquired taste. There are many 20th century composers (especially the serialists) I cannot stand. I can't hear the music in it. But Messiaen did get to me. Perhaps it's his "colours" or the Debussy-like chords.
As for ecstatic music, I wonder how you'd appreciate the music of Maurice Ohana, specifically "Messe", which despite being an operatic (or choral?) piece, I find calming.
I believe John Sichel's "Oiseaux Ordinaires" is homage to Messiaen's "Oiseaux Exotiques", though once again I'm not sure how much actual birdsong it incorporates.
I've always wondered how much of music's aesthetic is inherent, and how much relates to extrinsic factors. Normally you hear a piece and if you like it, you think, "hmm, that's good music". But maybe you only liked it because you're used to that type of music. So if you want to listen to music from a new genre perhaps you listen to it a few times, letting an appreciation percolate from whatever place we draw our musical inspiration. Then, because a lot of people say "this is a good genre; good music" and the genre is large with some shit pieces but also masterpieces, you come to believe that the genre has value. But some genres very few people come to appreciate, and that includes serialism, and I wonder... Is serialism lacking an inherent aesthetic, or is it just too different to easily appreciate? For example I played, and came to love, Schoenberg's "Six Little Pieces for Piano" (op 19). My interpretation was idiosyncratic; like no one else's. But looking on YouTube I can't find any performances that I enjoy or would recommend. So does my appreciation for this music reflect the blood and sweat that I've put into it, or does it reflect the beauty and understanding of the underlying musical theory? The question is: does serialism need to be played to be appreciated?
Great work. I also like l'Ascencion. I even try to play bits on the organ (not that I'm a good organist).
> I wonder how you'd appreciate the music of Maurice Ohana, specifically "Messe"
That didn't do it for me. I found it a bit too wandering, amorphous. I listened to some of his guitar work, which is much more concise, somewhat Webern-like. That spoke more to me. Then autoplay put on 12 etudes d'interpretation, which I predominantly found to be too "forced".
> Is serialism lacking an inherent aesthetic, or is it just too different to easily appreciate?
Composers, musicians, and musicologists have tried to push it long enough, and it never got hold, so I guess it just can't work apart from some gimmicky use. It's too rigid. E.g., the dynamics, rhythm, melody and harmony of a piece should be related to each other, but in serialism, they're simply tossed around as if every preconceived change between pp and ff and then mf and then a bunch of sfz will always be musical.
Music thrives under limitations, because it's basically repeated time, and limitations can provide direction. But if I were to start a school of composition that only allows one tone per part, I think nobody would be able to write a meaningful piece (except as a gimmick, again, by picking the instruments that fit with the chord you want). Some limitations are simply not musical, and I guess serialism is among those.
I don't care for the 12 études d'interprétation, but neither do I care for Rachmaninoff's Études-Tableux. I find both to be too pedagogical. Which makes no sense; according to Wikipedia they're meant to be "picture pieces". So I haven't always put much stock in études.
One other thing about whatever you want to call the contemporary continuation of classical music - you're right that there's often a lot going on. I've heard it described as "fragile" music: in contrast to pop songs that still work if you're on a train, if they're interrupted by an announcement, if you only listen to the second half, etc., a lot of this music is written to be listened to by someone who is relatively calm and undistracted, in a quiet environment. And honestly some of it has additional expectations of its audience, like a better than average ability to remember melodic snippets and recognize their transformations, or an ability to track "advanced" harmonies and key changes. But imo the general rule "90% of everything is crap" applies in this genre as well, and most of the pieces that everyone will speak of in glowing terms have a way of 'working' for most listeners without demanding advanced education, study, or above average musical-listening abilities.