purchasing recent recorded CD's. And recent is: not before 1990, but preferably after 2000. I myself bought some CD's last weekend.
125th Anniversary Album Strawinsky with Violin Concerto. Recorded 2006 at the Abbey Road Studio, London. Listening to this concerto I learned how far a violin could go with producing sounds I never thought possible.
Also on this CD is the Rite of Spring, great recording 1967 edition. Again one can learn form the sound of it.
I already had the fairly new Symphonies of Prokofiev, Berlioz (Symphony Fantastique), and new is the Rachmaninoff CD with the 3 symphonies, also recorded within that time-span.
One should do this, not only for learning and enjoying the music, but also for the Academy of Orchestration (balance, articulation, etc.)
... and of course I am applying these new "sounds" to my own Symphony. Question is: how, but I will find out to be as close as possible.