Finding an orchestral piece that you really like, and purchasing the study score will go a long way in your education. Most of the major works are now in the public domain, so the scores are quite cheap (for example, The Rite of Spring at $9.95, is a steal). Once you have soaked in that score move on a different composer, or era. Keep in mind that the art of orchestration didn't really begin until the 1800's. Bach, Mozart, Vivaldi, etc, tend to be relatively simple examples of what those instruments are capable of, both in color and combination. From Beethoven, through the Romantic period, and into the 20th century there is a vast library of genius to get lost in.
Another must have is a good orchestration book. There are some great choices out there. If you really want to get knee-deep into it, I recommend The Study of Orchestration by Samuel Adler. It's pricey and you will need the CD-Rom companion set which doubles the price. A more affordable option that is geared towards a beginner would be The Technique of Orchestration by Kent Kennan. This package includes audio CD's with the hardcover for a bit more than the cost of the Adler textbook. If those excursions to Cochella or Bonnaroo have left your bank account balance looking like your shoe size, Rimski-Korsakov's Principles of Orchestration is your answer. It's under $15 and covers ranges of instruments, the tonal shades within those ranges, and colors of instrument combinations. This is an art that will take some time to master, but in the process you will grow as a composer and as an orchestrator.
For those of you that haven't listened to a lot of orchestral music and lack favorites, here are some recommendations for you:
- Music for Strings, Percussion, and Celesta: Bartok - An isolated example of the string section and all it can do, plus the eerie use of percussion. Not public domain yet, so the score won't be found for $20, but it's worth every penny.
- Til Eulenspiegel, Zarathustra, and Ein Heldenleben: Tone Poems by Strauss - Excellent examples of brass writing. All three pieces available in one book.
- Petrushka: Stravinsky - You can get familiar with the woodwind family with this score. I spent an entire semester in college studying just the woodwinds.
- Pictures at an Exhibition: Mussorgsky - Originally composed for piano, later orchestrated by Ravel. The Eulenburg edition of the study score has both the orchestra and the original piano part together. It's fantastic to view it this way and see the choices Ravel makes.