I was very privileged to be hand-picked to be part of a small Master Class taught by
Roy Harris. It was rather amazing for me because I was a sophomore and most of the people in the class were graduate students, but my Theory teacher thought very highly of me and had heard some of my nascent piano pieces, so he got me in. Roy was rather old, but he talked a lot about modes and his Third Symphony and his wife (Katherine? am I remembering that correctly?) wowed us with her piano playing. Roy would call out a composer and piece and Katherine would just lay into it, no holds barred. It was a great experience. I still remember him comparing various modes to different colors, acid-head that he must have been.
So many wonderful composers, so little time--these just off the top of my head:
Ralph Vaughan Williams: pretty much anything, but especially the 4th symphony
Prokofiev: pretty much anything, but especially the 5th symphony (most especially as conducted by Ormandy)
Faure: Requiem
Durufle: Requiem (oy, I'm getting depressed)
Ravel: Mother Goose, Le Tombeau de Couperin
Brahms: any/all, but the 4th conducted by Walter can not be topped. The recent reconstructions of the original, smaller symphony orchestrations are very interesting, if not quite as grandiose as the ones we're all used to hearing
For those who like Copland/Harris, I highly recommend former University of Utah Composer in Residence Ned Rorem, who has written some great chamber music, notably his Water Music.
And just to be a little outre, I think Frank Zappa's orchestral/chamber stuff is the equal of Varese's (Edgard that is, not Sarabande
).
