Fiction is very greedy. It will take all you know and then some. The first novel I tried to write, I was struck by this - the appetite of the blank page for ever more information, ever more data. An empty book is a greedy thing. You are right: You wind up using everything you know, and often more than once.
That feels natural to me, singing in a small group of people I just can't do. You'll never hear me sing at a dinner table or anything, but this feels kinda natural. I've done it many, many times. So, and also, the pressure's off me cos I'm not singing on my own. I'm just doing a few harmonies with my stuffed nose.