If you've seen last year's hit film (500) Days of Summer, you know that music plays a central role in the story; as in most relationships, songs are connectors that glue a couple together, that reveal something important about personality and taste.

For Scott Neustadter, who co-wrote the acclaimed (500) Days screenplay with Michael H. Weber and will be guest blogging for West Coast Sound all of this week, scripts literally begin with music. He starts writing when he plugs his earbuds into his head. “I've never been able to do it without music,” he says. “When I get into writing funk, it's almost always because I haven't heard a new song that's exciting me in a while. And then I'll come across some song that I've never heard before and then it's like, 'Ooh, here we go,' and the juices get flowing again. It's nice.” His current faves: Camera Obscura, Empire of the Sun, “and then, of course, the Phoenix album is no joke.”

Much of the soundtrack to (500) Days, in fact, came about during the writing process, which isn't the way it usually works. Normally, songs are woven into the movie after the script is finalized. But Neustadter says that song placement had to be considered from the start because the music is very specific to the scenes, and a lot of it is based on his experiences.

As a result, the writers worked closely with director Marc Webb. “The song that they would use that I wrote into the scene was the song that was playing in the scene when it happened in real life,” explains Neustadter. “The Smiths scene in the elevator is what happened, verbatim. And it was that song.” That the two connect over “There Is a Light That Never Goes Out” doesn't bode well for the couple, played Joseph Gordon-Levitt and Zooey Deschanel, laughs Neustadter: “Oh my god. If it's a Smiths song that bonds two people together, it's going to end badly. That is not going to be a relationship that's going to work out. It's a harbinger of disaster.”

Another telling scene involves a karaoke bar, and, as in real life, what the two characters decide to sing says a lot about who they are as people. Neustadter says that the songs in those sequences came about differently, and that the selection process was not without its bumps. “Joe and Zooey got to pick their own karaoke songs just to make them feel more comfortable,” he says. “Joe wanted to do 'Here Comes Your Man' by the Pixies, and Zooey wanted to do 'Sugartown' by Nancy Sinatra. But she also wanted to do Linda Ronstadt's “Different Drum,” and I was like, 'No way … we have to talk about this.' Because if you listen to the lyrics, it's exactly the movie, and it's exactly what happens. And it was way too early — way too early — for her to be singing that to him. We're stepping on everything. Thank god they listened to me, or otherwise I would have really panicked.”

Spoken like a true music freak.

Neustadter will be blogging all week for West Coast Sound. A round of applause, please …

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