If you visit my website, you'll see that on each of the pages for my books I have a playlist included. These are the songs I first listened to when I started working on each book. They do grow over time. Sometimes I'll remove songs from the list if a certain part of the story changes between the original idea and the final product. Sometimes I add new songs in during revisions. But I always go through my iPod and find songs that speak to me in some way for this story.
For example, my book Surfacing is about loneliness and recovery after a huge loss. When I first got the idea for the story, I searched for songs that fit that tone I wanted. Most of the songs on Surfacing's playlist reflect this somber, detached mood: "The Sound of White" by Missy Higgins, "Go" by Hanson, "From Where You Are" by Lifehouse, "Please Do Not Let Me Go" by Ryan Adams, "Name" by The Goo Goo Dolls.
On the other hand, Troy High, a modern day retelling of the Trojan War, includes a lot of action with pranks between the two schools in the story and so its playlist has a completely different tone. "Bad Reputation" by Joan Jett & The Blackhearts, "I Think I'm Paranoid" by Garbage, "Vindicated" by Dashboard Confessional, "Local God" by Everclear, among others.
Writing is very visual for me. I find pictures of people who look like my characters so I can keep their images in front of me while writing about them. I collect pictures of the area where my stories take place, and even pictures of homes that look like the ones my characters live in. Music is a visual aide for me because it helps me to fully imagine the scenes in my head. Sometimes if I'm stuck in a certain place, all it takes is for me to listen to that book's playlist to get the scenes in my mind. I can't listen to the music while I'm actually writing because I find it too distracting, but I do listen to the playlists a lot while brainstorming and especially when I'm first imagining the plot and characters.
I know I'm not alone in this! I've seen several other writers include playlists on their sites. What about you? Do you use music to help in your writing? Or for readers, do you find that certain songs remind you of books you love?