As I perused the soundtracks section of a local music store last week, I stumbled upon the Grey's Anatomy Soundtrack, Volume 3. Having apparently missed Volumes 1 and 2, and, admittedly, having only caught the actual show on one or two occasions, I had little notion of Grey's musical backdrop.

But I went in with my assumptions. After all, this is the show that brought "McDreamy" to our national lexicon. Wouldn’t it follow that its music would be lighthearted, upbeat, and, well... McDreamy?

That’s when I flipped the CD over and read the names of the artists on the back.

The Bird and The Bee? Paolo Nutini?

These relatively unknown critical darlings were representing perhaps the most popular primetime soap on television?

Soundtracks have long been an avenue for new artists to get their music into a bigger forum. But over the last few years, the public's relationship with the soundtrack genre seems to have shifted. No longer is a soundtrack just representative of a film. No longer is it just another opportunity for big-name artists to cash in on lucrative projects (you should be hearing Aerosmith’s "Don’t Want to Miss a Thing" or Berlin’s "Take My Breath Away" right about now). No, soundtracks now increasingly serve a more practical public service as well: More and more are offering a crash course in great, albeit obscure, modern music.

Naturally, it's impossible to define an exact moment in which this transition took place. Perhaps the soundtrack to 2004’s Garden State helped legitimize the genre as a way of accessing new music. Zach Braff’s self-described "mixtape" that-went-on-to-win-a-Grammy got music lovers humming Frou Frou, Iron & Wine, and The Shins almost overnight.

But it would be a mistake to assume that new modes of marketing (such as inclusions in soundtracks) have single-handedly expanded America's musical horizons. Even more fundamentally, the digital world has increasingly diluted the old notion of "mainstream music." With many music fans almost surgically attached to their mp3 players, radio’s influence has faltered. Creative marketing mixed with digital purchase options lets listeners define for themselves what should be deemed "mainstream."

What's that you say? You were watching an Old Navy commercial and heard The Bird and The Bee's "Again and Again?" I’m sorry—did you say you heard the new Lifehouse single in a Chevy ad?

What once would have instantly earned these artists the "sell out" label is now just plain smart. Ads have become just another music venue. The hope is: Maybe you'll be sitting at home wondering who sang the song in that last commercial. Maybe you'll look it up online and purchase an mp3. Maybe you'll even become a fan and attend concerts and such. Especially with users' abilities to now purchase songs individually, listeners are encouraged to explore new music without having to make the commitment of buying an entire album.

What's more, established artists are recognizing the changing scene and making different career choices for themselves. Take, for instance, Radiohead's newest release, In Rainbows. With their EMI contract already ended, the band initially chose to release In Rainbows digitally in October 2007. Not only could fans purchase this new album online, but they could also decide what price they were willing to pay for it. This example perfectly illustrates an established band sticking it to the Old Establishment. Nope, it's not just about the up-and-coming artists determining new approaches for getting in the biz – it’s also about reinvention for longstanding commercially successful artists.

To boldly declare that the music world is changing would be an old cliché at this point. And besides, record labels still play hugely important roles in promoting and booking many commercially successful artists. Nonetheless, it is interesting to observe the swelling of music trickling onto the scene via alternate paths: websites, local fanbases, independent labels, and so on. Ultimately, listeners benefit: By being exposed to a larger spectrum of music, they have greater opportunity to be eclectic in their tastes. They can take what they like from the popular and obscure scenes: a pinch of Beyoncé, a smattering of Butterfly Boucher and Alexi Murdoch, mixed with a dash of Tim McGraw and a hint of old school classic rock.

With all this being said, the reason behind the soundtrack genre’s current trends is quite obvious. It is artistically relevant for a popular show like Grey’s Anatomy to relate to its viewers through hip, offbeat – and most importantly, non-"mainstream" – music.

In a way, you might say that being "non-mainstream" is the new mainstream.

By Chelsea Fogleman Contributing Writer