Character Development: Yes, even though I have a close or exact idea of what kinds of characters I want, sometimes I need that boost or mind setting for some. For example, during the early development stages of Balthazar, I stumbled across the song Headstrong by Trapt. I knew what I wanted Balthazar to be like, but this really helped me grasp the idea of his mentality.
Motivation: When I feel that I'm not up to the task for the day or I'm just trying to get in the zone, music has been the answer. I sit back, play my playlist, and just go. If I'm trying to touch those buried feelings needed to make a scene feel more emotional, I find the songs that can speak the closest to what I'm looking for. I'll lie down for an hour or so and listen to classical music to see if I can touch and feel what is entering my skull before putting that on paper.
Inspiration: Sometimes I get lost on what angle to approach. This tends to happen more often than I like to admit when it comes to fight scenes. But all that goes away when I listen to the right kind of battle-like instrumentals. And sometimes, even lyrical songs that were never meant to inspire fights. (Didn't I tell you I interpret songs my way?) Inspiration tends to birth many different paths of writing for me. New chapters, new characters, new dilemmas, and sometimes alternate endings that beat or rival my original designs. Inspiration may actually be one of the most important things that come from me listening to music.