Heidi is doing a series of posts on preparing for Nanowrimo and has just done an interesting one on making the soundtrack for your book.
I too am a soundtracker, which I've talked a bit about previously here. When Heidi said her soundtracks are around 100 songs, my first response was "whoa, long". Then I wondered why. When I check my soundtracks, they're all around 25 - 30 songs (I have one that's about 19 but that's for a book I've only done a little bit of writing on and I imagine it would grow once I got into it more and the longer ones are for books that are part of a series, so there's maybe more going on in them). So mine are about a quarter of the length of hers. Process is a funny thing. I like my soundtracks the length they are so that I get lots of repetition to trigger my world fast. And so that the music becomes almost a background sound to me over time.
Like Heidi, when I sit down to soundtrack a book (which is one of the first things I do, along with a collage), I open up iTunes. I usually have one or two songs that the girls just know are right and then I randomly throw other things into the mix by instinct. Also like Heidi, I have a good sized iTunes library plus a bunch of other cd's that I've never bothered to load into iTunes, so I have a good starting point.
A soundtrack song can be included for:
1) Mood or setting of the book
2) Sense of a character
3) Scene mood
4) Character story/background
5) A particular lyric that belongs to either the hero/heroine/antagonist or the story idea in general.
I tend to favor music with words (lots of rock and pop) but will throw in instrumental (often from movie soundtracks) or ambient as well. There's probably usually more character stuff than mood stuff, and there's always at least one song for the antagonist. Once I have my initial list, I'll write to it for awhile and see what I think. Songs get moved around so they suit the flow of the story better, they get deleted because they jar me when they come up, they get added because I hear something new that fits (usually a character song) or because something is missing. When I first started writing I used to listen to whole albums for books but these days that doesn't happen. I'll often have several songs from one album in a soundtrack because they fit but the last time I wrote to a whole album was probably six years ago.
The great things about downloadable music is that you can just buy one song if you need just one song. The previews in iTunes are also a good way of finding stuff when you're missing something (for example, for my Witch book, I needed a lot of dark electronic music. Not something I listen to very much, so I went googling on the internet then came back to iTunes. If you're not in Australia you can probably also try things like Last.fm and pandora radio to find music and the Amazon mp3 store. But if you're an Aussie, iTunes is probably the easiest way to instant music gratification (and single song purchasing), though other online music stores exist. Asking your internet peeps for recommendations is also a good way to go.
Once I've got my soundtrack pretty nailed down then I listen to it almost every time I write on that book. Somedays I just need silence (rare) and sometimes I'll use a concentration aid if I'm really tired (again rare but check out things like High Focus from BrainSync) but my soundtrack is the fastest way for me to connect with my story world. I'll even play it in the car or on the iPod at work if I'm mulling over a story problem in the back of my brain. Sometimes I listen to the whole soundtrack, sometimes, I listen to just one song over and over for a particular scene but I stick to those songs to trigger the world for me. I'm a fairly strongly aurally focused writer. I hear what the characters are saying before I see them. Some writers say it's like watching a movie in their head. For me it's like watching movie with a blindfold on. I can go back and concentrate to see what's going on but it's all about the dialogue and the rhythm of the words, which is why soundtracks work well for me I think. YMMV.
I often find towards the end of the book, that I do another soundtrack, much shorter, five or six songs and write the last 80-100 pages to that (I usually write those pages fairly fast). Those songs are usually a lot more about the mood and feeling of the last act and the build to the climax. They're often a bit left field and are more likely to be from only one or two artists or albums. My werewolf demanded chunks of Pirates of the Caribbean - At World's End interspersed with Pink for the ending of the last book. And my Witch wanted Dixie Chicks from Taking the Long Way. She wanted that all the way through the revision as well which was fun. But play me one of those songs and she's there in my head, so it works.
So soundtracks are worth a try in my opinion, though for some people the thought will probably make you run away screaming. I've always listened to a lot of music, I used to play an instrument, I used to listen to music while studying (which made my parents somewhat nuts), I did various forms of dance, so I think there's a part of my brain keyed to music both as an emotional trigger and a sort of "work now" trigger (I also need music for exercise for much the same reason). As soon as I sat down to write when I decided to finally get off my butt and write a whole book, I turned on the music with the word processor. If you've never tried it, give it a go, particularly if you're going to try Nano which pretty much needs as many tricks as you can to come up with to keep producing 1600+ words a day.