My Opera

After writing several small pop/easy listening style pieces, I have decided to go for it and write a larger work: an opera. I have the story down and I even named some of the characters after composers I really admire.

I decided to outline the story and journal about my characters before doing anything else. Now I am going to move along and start writing the libretto. The biggest obstacle for me is writing for orchestra. I am a pianist and I can write for piano, voice and a solo instrument like one violin or one flute. But a full orchestra? I have zero experience in that. Maybe if I write a piano part and then transcribe it to various orchestra parts that will make my life easier. I also want to know the little nuances like the difference between writing for C Trumpet vs. B Flat Trumpet? Any recommendations on how to learn about this? My community college does not offer an orchestra writing class.

Study orchestration before.

If what you say is true, your opera will be a failure.

I would consider writing an opera with just a few instruments.

You might want to take a look at/listen to some Britten.  His Noye's Fludde is for amateur musicians, mainly children, with a sprinkling of professional adults to hold it together.  It's intended to be something that can be put on in a church or town hall easily.  If you are comfortable writing for piano, voice, and a solo instrument or two, you could write a short opera for those parts plus one or two more to add to challenge yourself and learn from the process.  I wouldn't try to tackle full orchestra at this point, but think about what you want to accomplish musically, what you want to learn, and add one or two instruments to the mix that will best serve your goals.  Look at this as a learning exercise, rather than a formal work, and use the writing process to help direct the beginning of your study of orchestration.  Keep in mind that the prospects of attracting any professional musicians to work on this project with you when you are still learning as a composer, are slim.  Even if you pay them, they may not want to be professionally associated with a beginner effort.  Professionals are in demand.  You are unlikely to be the best offer they have to add to their resumes on any given date.  But if you keep the number of players very limited, the piece short, and the parts very simple to learn, that gives you the option of calling on a handful of amateur friends to help you stage a performance for your own enjoyment so you can see what it all sounds like and learn from the experience.  Who do you know who has free time and loves you dearly?  Write a part with them in mind that they can learn in a few hours.  Make sure the whole thing can be pulled together in as little rehearsal time as possible and friends will be more likely to think it would be a fun use of their weekend. 

Option two.  The college I graduated from used to have a weekend of 24-hour plays.  The theatre students, plus any friends and roommates who could be convinced that this would be fun, would divide up into teams, and each team would write, rehearse, and put together props and costumes for a short play.  Day one was play writing and rehearsing day.  Day two, all the plays were performed.  Attendance was open to the whole campus, but each group was guaranteed that at least the other teams would want to watch.  If you are a student, you could propose a similar music composing weekend, with everyone writing and performing each other's works.  When it's a group effort, rather than just one person, (you), trying to recruit performers and an audience, the activity generates more enthusiasm and less cringing.  It's easier to laugh off the bits that inevitably turn out boring or fall apart completely (since you are just starting to learn), when you have company.  

Here's the wikipedia bit about the forces required for Noye's Fludde:  

For the first time in any of his works involving amateurs, Britten envisaged a large complement of child performers among his orchestral forces, led by what Graham described as "the professional stiffening" of a piano duet, string quintet (two violins, viola, cello and bass), recorder and a timpanist. The young musicians play a variety of instruments, including a full string ensemble with each section led by a member of the professional string quintet. The violins are further divided into parts of different levels of difficulty, from the simplest (mostly playing open strings) to those able to play in third position. The recorders should be led by an accomplished soloist able to flutter-tongue; bugles, played in the original production by boys from a local school band, are played as the children representing animals march into the ark, and at the climax of the opera. The child percussionists, led by a professional timpanist, play various exotic and invented percussion instruments: the score itself specifies sandpaper ("two pieces of sandpaper attached to blocks of wood and rubbed together"), and "Slung Mugs", the latter used to represent the first drops of rain. Britten originally had the idea of striking teacups with a spoon, but having failed to make this work, he sought Imogen Holst's advice. She recalled that "by great good fortune I had once had to teach Women's Institute percussion groups during a wartime 'social half hour', so I was able to take him into my kitchen and show him how a row of china mugs hanging on a length of string could be hit with a large wooden spoon.

Britten also added – relatively late in the process of scoring the work – an ensemble of handbell ringers. According to Imogen Holst, a member of the Aldeburgh Youth Club brought Britten's attention to a local group of bellringers; hearing them play, Britten was so enchanted by the sound that he gave the ensemble a major part to play as the rainbow unfolds towards the end of the opera. Several commentators, including Michael Kennedy, Christopher Palmer and Humphrey Carpenter, have noted the affinity between the sound of Britten's use of the handbells and the gamelan ensembles he had heard first-hand in Bali in 1956. The scarcity of handbells tuned at several of the pitches required by Britten in the opera was to become an issue when the score was being prepared for publication.

Basically orchestration is about balance; instrument typical ranges, articulations and characteristics; chord layout for different sizes of orchestra at different volumes; emphasising instrumental entries if necessary (at different volumes); the use of solo passages within the orchestra; how and why you 'double' instruments - and a few others.

Best is to get a reference book, maybe one on how to arrange from piano for different sized orchestras, and a few scores to see how it's done. Choose fairly conventional scores at first so they're easy to read and reconstruct in your mind. They aren't expensive. Beethoven is good for woodwind writing (although he tries it on with oboists a bit). He isn't good for standard choral writing. I'd suggest his 3rd (Eroica) and 9th (Choral) Symphonies; maybe Elgar's Enigma Variations. Only as a start. You may wander into the more exotic as you go.

My orchestral reference books are a bit old. For arranging from piano, I'd suggest Gordon Jacob's 'Orchestral Technique'. Expensive if you buy new but his book is available sub-£10 on Abebooks. It  may be enough alone, giving the important characteristics of instruments as it goes along. I also have Piston's 'Orchestration' which is a good reference for instruments, their characteristics, fingering (with woodwind) and on, and contains examples of their use in all kinds of established scores - but it's gathering dust. Another expensive book and there are others all hideously expensive. 

It may be enough to get a couple of scores to look at the layout and conventions, then use Wikipedia for the instruments. The Gordon Jacob deals a lot with balance which is easy enough when explained - not that orchestras will necessarily produce what you want. 

You might want to venture into the exotic - but then if you're writing an opera, how exotic do you want to be? Besides, you can learn how to do exotic if you hear a sound you like then get sight of the score and find out how it was done.

If you can run to the expense you may think about digital publishing software that comes with adequate orchestral samples to try things out. Some of these can do useful things like lift out orchestral parts (which doesn't make them perfect: small staves for 'cueing in' passages aren't automatic as far as I can see.) Software takes time to learn but an opera is a major work and writing out parts could be a pain. I don't have such software. It's far too slow for composing but am thinking about it for finished scores, once I find one that does what I want it to. 

It's a big subject but making a start isn't difficult.  All the best.