Every creative person works differently, but no one starts from scratch. Even pioneers who are breaking new ground start from the place from which they were standing. Schoenberg, for example, came up with the idea to eliminate a pitch center (you know how most songs seem to have a home note?) but in order to come up with that he needed hundreds of years of music history. In reality, he simply took what was already going on to its logical conclusion (long story for another post).
The way I compose is a lot like the way I built lego spaceships when I was a kid (and still do every now and then!). I started with the same 4 block 2×4 template, and built onto it until it was something I’d never made before. It’s the same when I write. I start with something I already know, and just keep adding to it. I never try to be original. I’m a strange enough person as it is. I don’t need to try to be different since nothing I’ve ever written has ever really sounded like anyone else (something I’m trying to cut back on, actually). The more you try to sound like a precedent, the better. You will end up sounding different no matter what you do, I promise. Let previous masters pave your road to your own mastery.
It really all comes down to this brilliant C. S. Lewis quote: “Even in literature and art, no man who bothers about originality will ever be original: whereas if you simply try to tell the truth (without caring twopence how often it has been told before) you will, nine times out of ten, become original without ever having noticed it.”