For me it differs from project to project. Lately I like to have something to inspire a mood. But there are times -- when I'm more clear on whatever it is I'm setting out to do, or more intent on creating that mood from the ground up -- when silence or white noise is better.

I totally get the word melody thing. I imagine that's part of what I'm reaching for in "I need a mood" mode. Never thought of it that way before.