What would Armageddon be without Aerosmith's I Don't Want to Miss a Thing? Or Spiderman without Nickelback's Hero? It's amazing how we could hear a song 40 times on the radio and never have it stick, but once it's applied to the right scene in a movie or show, the song seems to stay with us.

For example, Snow Patrol was virtually unknown until their song, Chasing Cars, was played on Grey's Anatomy's season two finale. The next day, the single became the number one downloaded song on iTunes.

Alexandra Patsavas is a music supervisor, and the genius behind the song selection for shows like Grey's Anatomy, The O.C., Gossip Girl and Mad Men. She also did the soundtracks for the Twilight saga.

"(The music) can really create a world, so that the moviegoer is dropped into a world ... and once you hear a song from a movie, to be transported back to that scene is the goal," Patsavas explained.

She was nominated for a Grammy Award for Best Soundtrack for Grey's Anatomy in 2007, and more recently for an American Music Award for Best Soundtrack for her work on the third instalment of the Twilight saga, Eclipse.

The music selection process for a blockbuster giant like Eclipse can be quite lengthy. First, Patsavas reads the script and becomes familiar with characters before the movie is even shot. Once the footage is assembled, the music supervisor spends a lot of time in the cutting room with the director. It is then time to start contacting artists and creating specific songs for specific scenes.

Patsavas said she spends hours listening to music, trying to find the perfect fit. "The most challenging part was the great good fortune of having so many good submissions and a limited amount of sound spots in the movie, which is a fabulous problem to have."

All the songs for Eclipse were written specifically for the movie. Any Twi-hard fan knows Eclipse contains the big showdown scene against the evil vampire army. "I think a lot of this soundtrack definitely reflects that battle, it has a lot of edge," said Patsavas.

The soundtrack features music from already well established artists like Metric, Muse, Cee-Lo Green and Vampire Weekend, but also has equally fitting songs by newer bands such as Eastern Conference Champions and UNKLE. Patsavas described the song-finding process as a "creative, fluid process. I think it's just the right song, the right vocal quality, what a director has in mind for a scene. Is it a female vocal? Is it electronic?"

For anybody with an interest in music production, this would be a dream job. Patsavas' career requires an extremely cool indie rock taste and a flare for fitting music perfectly into any situation. Whether it's petty drama between Gossip Girl's Serena and Blair, or a battle between vampire and werewolf, she's your lady.