After doing a lot of deep listening, the next step to familiarizing yourself with the orchestral instrumental palette is to read. Find scores of works you can listen to and read along with. I’ve found a wealth of free digital scores at these two sites: IMSLP , free-scores
IMSLP has a ton of public domain (generally meaning old) works to download in pdf, sometimes multiple editions of the same work. There are publishers who will also sell you a hard copy of many classic works if you want them on paper or more contemporary things that aren’t public domain. If you want John Williams then you can get conductor’s score editions from Hal Leonard. Omni Music Publishing puts out wonderful full scores of soundtracks that could be of great interest to you. Other than that you might find that most soundtrack scores are not available. With some experience you could undertake a transcription yourself from listening to the audio, that’s an excellent exercise to do even for things which are available in print. You can try your hand at it first and then compare to a published version to see how close they match. That is getting ahead of ourselves though, let’s bring it back to score reading.
I’m not digging deep into the theory here, I’ll stick to mostly the orchestrating aspect, but if you want to brush up on your theory I’ve found this reference to be so good: Music Theory for the 21st Century Classroom by Rob Hutchinson. It really has so many principles demonstrated by example in a superb way. Do read through it or go to it as a reference whenever needed. It’s organized rather well to just jump into whatever section you need.
You should study any pieces you love or things that are in a direction you would like to go yourself. People will ask “what is best to study for this or that?” and I can’t tell you because I am in no way a knowledgeable reference for all things orchestration, I just note things I hear that I like and I seek those things out. I think you should do the same for whatever gets your heart beating. Don’t get too caught up on what others think, or what might be considered the standard. By all means investigate the greats but don’t worry much about having different opinions than others, variety brings richness to the world.
Reading through the score while listening is good but it’s not enough for me, there is a lot going on that can’t be absorbed just in real time as you listen. I sometimes start out by doing an initial read through as I listen but then I will go back and analyze the score in more detail, deconstructing the harmony, voicing, and whatever other elements that catch my interest. I have done 2 stave reductions before too (writing all the notes on one grand staff), which is a great exercise to see how all the elements come together and what the harmonic function of each voice is within the context of the whole group.
To further your ear training and instrument spotting you can see exactly who is playing and hear simultaneously what that sounds like. Through this training you can develop the wonderful corollary skill of being able to hear a desired sound in your minds ear and be able to orchestrate it successfully to achieve that imagined sound. As I read through the score I also pay close attention to how sections are balanced. You can look at this multiple ways. Check how the balance of harmony is achieved within a section, some passages may have all the harmony covered within the string section for example but then other passages may have the harmonic support spread between different instrument families. You may have strings carrying the melody in unison or octave doubling and brass and winds filling in the support underneath. All different scoring combinations (and there are endless ways a tune can be orchestrated) will give different sounding results and many of them won’t be very good sounding so as you hear what works and sounds good you should pick it apart to figure out why certain arrangements work so well to give a particular desirable effect. It may be related to how an instrument stands out from the rest, it may be how instruments blend together. There are so many emotive possibilities.
You can find a large number of orchestration manuals and reference books if you look for them. You can also find university classes on this stuff if you need that format. I have been through some music literature and theory courses at the university level but I didn’t go through any composition specific courses or in class intensive symphonic analysis. I have been doing that part of it on my own after getting a solid music theory education and lots of practical experience in choirs, bands, and various ensembles. There is so much information available that a motivated learner can put together their own excellent curriculum on the subject. These posts of mine are not a course on orchestration, but just a log of some of my thoughts, experiences, and advice to others who want to go through a similar journey. Tailor your own experience to get the most benefit for yourself. I’ll next do a few posts about some of the pieces I have read through and my interpretations and reactions.