In a sense, I think that all creative pursuits are served well by the type of "brute force" you're talking about. You write/play/draw something, decide if you like it, and then work from there.

I think you are absolutely correct.

In the case of your melodies, what happens if you just "hum something?"

I can hum things, but they sound rather classical and banal, like Eine Kleine Nachtmusik (which I hate with a passion). I'll try again when I'm in a different mood... it's been a while since I last tried to compose.

This is how I write most of my music. Every once in a while, a melody or chord progression will just show up fully formed, usually on the subway or in the shower, but it's rare. Most of the other songwriters/composers I know work similarly. You say you don't hear new music in your head; a lot of the time, I don't either. I hear it as it comes out of my mouth or speakers in real-time.

Interesting. I guess I always assumed that others had some capability I didn't.