I mentioned Messiaen in some music thread a while back and him being my favourite composer hasn't really changed, particularly his Quartet for the End of Time, which he wrote as a prisoner of war during WW2. (https://www.youtube.com/watch?v=FVojbUao2ww&list=PL8oAJzPXGW51pG9YuP3Y-RTWznVVxUjs3&index=1)
There's an aimless sort of wandering quality to the first movement that I've never seen accomplished in any other piece of music; among other things Messiaen uses isorhythms to make it feel like time has just been suspended. the piano repeats a 29 chord sequence over a rhythmic pattern using 17 notes. These numbers are both prime (being coprime would've sufficed), so the two patterns don't ever sync up during the piece, and you're left with this bizarre case of listening to the same thing repeatedly yet it's always malleable, unsettled, and wandering about. overall the quartet is a great listen if you're feeling depressed, especially the popular 5th mvt (https://www.youtube.com/watch?v=fbijWH_NB60&list=PL8oAJzPXGW51pG9YuP3Y-RTWznVVxUjs3&index=5)
I've also been a really big fan of Shostakovich, his music was written under Stalin's totalitarian regime and the isolation and contempt he held was expressed incredibly through his music, especially in pieces which he wrote but never published since they would've put his life in danger, like Symphony no. 4 or his Violin Concerto.
Though I think my favourite moment in all of his works is at the end of his Symphony 5, mvt 3 (https://www.youtube.com/watch?v=EtTaDwMpdkQ&t=773s)
where he has the harp (playing harmonics), the celesta and the violins accompanying those two. the combination is such a unique sound, this blend of eerie, ghostly, sad and elegaic emotions all at once. the movement ends with a picardy third which feels a bit clichéd and overdone by this point in the 20th century, but it's still comforting and we have to understand the symphony was written in the context of his work having been denounced harshly in the Pravda for being too "complex" "formalistic" etc...