I'm in the middle of a fascinating book, titled Parallels and Paradoxes. It consists of a series of conversations between Daniel Barenboim and Edward W. Said on music, culture, and politics. A sample, from Barenboim:

I still think the greatest sense of isolation and removal from anything, for me -- but this is very subjective, and I do not claim this to be objective -- is in late Beethoven. If you look at the Grosse Fugue, you look at passages of the Missa Solemnis, and you look at the Diabelli Variations or the last three piano sonatas, this is total isolation and removal from the world, much more so than Schoenberg.