MTV Networks (NYSE: VIA), now better known for creating series like The Hills than bringing the world the next Thriller video, is launching a new social net site tomorrow called Soundtrack. The company previewed the site at a small briefing in a plush, living room-like setting at its offices in the Viacom building Tuesday afternoon. While executives sought to avoid any comparisons to MySpace Music or Last.fm, the main point of differentiation is that the song and artist selections on the site are based largely on tunes used within shows on the cable net.

MTV JV Rhapsody America plans to start selling songs for download to own through Soundtrack next month. Asked if the site is going more for promotional or as a direct revenue source to sell music, Brian Graden, president of entertainment, MTV Networks Music Group, emphasized that the site will remain in beta for some months, adding “We want to see how the site is used first before we make any determinations.” The same goes for whether the site will be ad supported, said Amy Doyle, SVP of Music & Talent for the network, adding that the company will consider advertising further down the road.

In the meantime, David Saslow, SVP Video Content, Production, & Programming for Atlantic Records, told me that so far he’s impressed with the site and does expect to see it yield actual sales. Saslow: “I do think it will impact sales. We noticed immediate results with our new act, Carolina Liar, after songs were used on The Hills last season. There was a listing on mtv.com of the songs + scenes used in the show. This site is that idea on steroids.” More on Soundtrack’s features after the jump.

Some of Soundtrack’s features include:

-- A music discovery “wheel” that tells fans what day, show and time they can hear their selected artists. The wheel allows users to search for music currently playing on-air, upcoming in the next 24 hours, and previously played in past show programming dating back to Soundtrack’s launch.

-- MTV is starting with 2,300 band profiles and hopes to increase that number quickly. The bands, a mix of major label and indie, can raise awareness by creating customizable Soundtrack profile pages where they can stream music, videos, promote upcoming events and encourage fan support with tools such as a “vote for me” button called “Support By Sound.” The Soundtrack community will be able to elevate the Soundtrack rank of their favorite band’s songs by listening or voting for them.

-- A Soundtrack ranking system features “Top Artists” and “Top Songs” in the community and provides high-ranking emerging artists with direct access to MTV music supervisors, who will be listening to the online community, observing bands rankings and hand picking new artists to play on MTV on-air programming.

-- Auto-generated playlists around highlighted show moments will be featured on Soundtrack, such as “best party songs” from My Super Sweet 16 episodes.