How does one go about composing? An idea just pops into your head or....?

For me, it helps to have a purpose, something specific in mind. What's the venue, who's in the audience, who are the performers? It also helps to have a genre, so I'll pick something - jazzy, atonal, romantic, whatever. A lot of these decisions are arbitrary, but I think it's important to have something in mind as a starting point.

As a teacher of classical composition, I'll lay it out for you:

Writing music is like learning to play an instrument. It takes time and work to make a go of it, and there's a lot you have to learn in order to make a go of it.

Much of what you pick up is gained through the act of doing it, which is something no one can teach you. Also, no one really teaches composition. A teacher may lay it out for you, but you have to take what's offered and make sense of it to yourself, and in your own way.

From the outset you're exposed to the composer's tools- Rudiments, Harmony, Counterpoint, the latter two of which get into the basics of composing melodies, part-writing, and the basic principles of arranging.

From the outset I encourage my students to keep notebooks of their ideas. Every time they get an idea for a piece of music, they're either to write it down or record it. This serves a dual purpose- to get the student into the habit of writing (which is what it is to be a composer), and to get the student familiar with the ongoing process of recording ideas and examining and reexamining them. This, over time, produces a more and more refined and complex source of ideas.

That's what you need to know in order to get started.

For me the idea is the easy bit, whether it's a specific musical idea, or a "I want to write a string quartet" idea. Then you sit down and shape it into a piece of music.

I often hear an idea playing in my head when I'm starting to fall asleep and then I will have to get up and record the idea on my computer using a MIDI keyboard before I forget how it went and develop it as far as I can at the time. The next day I will listen to what I recorded and more often than not my reaction is "What was I thinking" but every once in a while I come up with something that can be used in a composition.

Hmmm...

Ok, there's different ways to start working on a work. And different reasons in reality.

Reasons

A1. The get paid reason. Simple as that, regardless of genre someone is paying you to compose something. You sell out your soul (ok, not really), and simply do it.

A2. The teacher asked me. Simple as that again. You should also learn something by composing the work your tutor has asked...

A3. My heart/mind/soul/nature/gawd gave me a tune. Simple as that. You, personally, WANT to compose a particular work. For whatever reason. Freedom of choice.

I find that a combination of A1 and A3 work quite nicely usually! Not very easy to do, but still..

Ways

B1. The sit on the piano bench and start playing way. Perfectly fine. You play until something clicks and comes up. You pick it up from there and develop it. If you have the theoritical chops you do so in paper ( + piano). If not you just sit on the piano until the next segment comes in mind.

B2. You sit in front of the computer and start adding loops. Perfectly fine as well. You get semi-ready loops, drums, bass and the rest and patch them up to sound nice. Very valid in some styles of music and perfectly alright even for Brian Eno.

B3. You find the external idea to kick you started. More difficult to do usually, it involves finding ways to use 'meta-art' knowledge and transfer values from somewhere into music. Perhaps it was an art painting you saw. Or a political movement. Or maybe it is the way the stars move. Whatever the reason you are pushed into composing by that, make your notes, your drafts, your symbols and your signs and then go further.

B3 v0,5. You develop a new system. Not twelve tone, not tonal, not quartal harmony, nothing. A new one. And toy with that.

I actually use all of the above, depending on circumstances. For computer games, I don't develop new pitch systems, but for academic work I did.

One of the most important factors, for an adult is the "who" is asking me to do it. Even if it feels selling out, it usually defines the style, the orchestral force, and the medium. A chamber orchestra will give you the exact forces, and normally you should also know what they tend to play: You can't go to the medieval orchestra of Shire (sayin' now) and give them aleatoric music. Or the opposite: Don't try the Boulez ensemble for some super tonal, Mozart style music.

For me, inspiration is the flick of the flame to get things started, the rest is hard work, knowledge, experience, etc...

I find poetry very inspiring. If I read a good poem a Michel Legrand melody finds its' way into my head then I have to find it on the piano. Like many composers I am also inspired by the beauty of nature, life , people, events and of course Chopin.

Mostly I have to say I am inspired by sound. If I play a classic piece my inner-ear says....hmm...that is a good key...you ought to write a song in that key.
that's me...
rada

Thanks for the replies. I find them all interesting.

I usually just start by considering what sound I want to create with the music I'm about to write. I consider styles, instrumentation, etc. Then I usually just sit down at a keyboard and noodle with ideas in the realm of what I'm aiming for until inspiration strikes. It's a remarkably effective method!

I'm not a composer but there are rules to stick with if you take some style. I think these rules serve as rough or tight guideline.