Well, the Quoran opened a bit of a can of worms with that question.
Some of the “worms”:
- Do you even need to know theory in order to compose?
- How do you advise someone whose biggest concern is to learn something fast?
- What styles are we talking? (I don’t think a single style of music exists that does not invite deep study, yet, not every style requires a lot of music theory – think punk for example)
- What background, musical skills (if any) and disposition does the questioner bring?
Learning to compose is not exactly a weekend project, yet read my post to learn:
- The three concise steps you can follow to get to your goal. Every time.
- How to speed up the process. (Not a flashy gimmick, yet it works!)
- A super easy composing technique you can try even if you have no background in composing at all. (And an example of a song that illustrates that technique. You are going to have to crank that one. I get chills every time!)