I am starting to learn about music theory and today it hit me how do classical composers such as Mozart and Beethoven are able to write music for instruments they don't play, such as (for example purpose) timpani or trumpet.
Is it all music theory or just that they where such genius they could intuitive compose for any instrument?
Why the past tense? How do classical (or rather, orchestral) composers write music? How does any composer write music for instruments they don't themselves play?
Although a composer doesn't necessarily need to be able to play an instrument to a high standard, they do need to understand the mechanics of the instrument, its limitations and capabilities. This isn't really a matter of genius, just of study and knowledge.
It's certainly not "intuitive" - it's learned.
Composers tend to collaborate with musicians and make changes based on their input. So, for example, they might give a score to a soloist, have them spend some time with it, then come back with feedback - "this part is impossible to play, how about we change it like this."
Nowadays composers can, if they wish, try multi-instrument arrangements out on a sequencer. It's still useful to be able to imagine how an arrangement would sound, and of course in the past that was the only way.
The archetypal composer sits at their piano; a very useful tool for trying out harmonies etc.
It would also make a great deal of sense to write mini-arrangements before expanding them to full orchestral arrangements. For example, score a segment of your symphony for a string quartet, and have a string quartet play it for you, as a prototype for the final work.
One point I would make in addition to slim's excellent answer is that theory is more to explain composition, not dictate it. In other words, talented composers write the music they do because they are translating what they 'hear' internally, not because the rules of music theory tell them that this is 'right'.
Although understanding theory is certainly a short-cut to being able to perform this translation, having a masterful understanding of theory will not make a good composer.
I am a composer and I agree with tpburch.
I am familiar with music theory but never studied it detail. Any good composer with a good ear will do a lot of those things naturally.
As a musician, I can figure out just about anything that makes sound and translate it accordingly.
Music theory or engineering won't teach you how to write good music. That all comes internally and we are just the translator or the vessel.
I believe many composers to have been gifted 1. The ability to hear a melody in their head and 2. Having a great ear to translate into existence.
Reading a book won't teach you to write great music. Listening to what's inside will.
Music theory is very key here. By understanding how notes together create consonance and dissonance, it's possible to compose some music without even playing, but to do this effectively most composers trained their ears to hear pitches, or at least to hear intervals( examples hearing a C note or a major third in a song).To do this an understanding of counterpoint helps.Counterpoint serves as the origin for modern harmony, so it can be very helpful. Beethoven, Mozart, and Wagner all studied Counterpoint from the same book, but that book is in latin and very expensive. While I could list a bunch of information here,Instead I'll give you some sources. http://en.wikibooks.org/wiki/Music_Theory/Counterpoint/Species_Counterpoint/In_Two_Voices look up counterpoint on amazon for books, or google 'Fux's counterpoint' (The book used by the said composers has been abbreviated some places) lastly, there is a youtube channel called 'artofcounterpoint' with some more information.
I can't play any instrument well, I play the piano but I would never ever perform in front of an audience, not even my own family, nor do I know much about music theory (I'm an autodidact), but I constantly hear music going on in my head and have been composing for many different instruments since the age of six. Some kind of schizophrenia, I guess, because I'm definitely crazy in some way. Maybe it was the same for Mozart or Beethoven, because I can tell that those melodies aren't the result of some fragmentised trial and error-improvisation process; there are continuous musical ideas behind their works. When I was eleven I started to work together with a producer to record some of my songs (I sing), and I've been using GarageBand and various notation programs on my iPad the last few years so that I could compose music wherever I am (I have zero patience, when I have an idea it will be gone if I don't write it down immediately, and then I get bored with it). Of course there needs to be immense amounts of skills and knowledge when it comes to creating great pieces of music, but I see it merely as the means to get the ideas out of one's head, and to get those ideas in the first place musical intuition is required.
Anyone can compose classical music the difference is what becomes a master piece and what not. There are plenty of boring/mediocre 'classical' composers & music even though the composers/critics may think it's not, yet when you ask someone who is the best composer the same names usually come out. Why? This is because they knew much about music in general including how to write it, how each instrument sounds like, keys & theory, etc... then you add a whole life time of experience and feeling it! and boom! you come out with a decent piece of music...
Think if you knew how to play guitar (or another instrument) you could come up with a small piece for 2 guitars or 4 guitars. If you are comfy in how they sound and each piece you could almost 'imagine' how 2 guitars would sound together although, many old composers had people that would come over (pupils even) that would play a piece just for a demo run. most composers like Mozart whom have a great imagination (which is one of the primordial keys) would write songs in piano or just writing the notes down, closing their eyes and 'hear' everything.
For the most part, the longest time in writing music for gifted composers is writing down what they already heard in their heads and its hard to do but not impossible. Think of a song you really like and close your eyes and attempt to hear it. Can you hear all of it or most? Well, same thing. Classical composers are just extraordinaire especially from centuries back because of the technology they had to work with and also because some symphonies have dozens of different instrument in different keys and voices!
It is rather insane when you think about it, but obviously doable. Also, music was a career. Hence you studied and worked your booty off daily and with so many musicians, you really had to be great in order to make it. Even the great ones struggled constantly, but they had music within their head constantly. Together with practice and theory and the drive to compose something great, you will hear symphonies. You can also build from templates in your head.
Example:
That probably sounds good enough and many would be able to 'hear' that in their heads. Now multiply that by a 100 if you are a decent musician and by 1000 if you were Mozart :D
