From the outset, the biggest appeal of social music platform Turntable.fm has been its synchronous listening in public rooms where anyone can become the dee-jay. Of course, turn back the clock six months, and Turntable probably didn’t see Facebook as a competitor. However, at f8 the social network launched Turntable-inspired synchronous listening and chat and went public with some big partnerships with the likes of Spotify and Rdio. At the time, Turntable could only grin and say “thank you,” but now the startup can reply with some big guns of its own, as it announced deals with the “Big Four” record labels — Sony BMG, Universal, EMI, and Warner — at SXSW today.

Launching last summer, Turntable saw quick, early adoption among music fans and tech media, but ever since the hype has dissipated, there have been questions hanging over the social music platform, like, “can it compete?” Without the blessing of the major record labels, many speculated that startup would be toast. But, today, that concern has obviously been put to bed, as the social music platform finally inked contracts with music’s bigs — after nine-months of white-knuckled, teeth-grinding negotiating.

Greg Sandoval at CNET originally reported the rumors that Turntable.fm was nearing a deal, and today Chairman Seth Goldstein confirmed those suspicions. Less than a year old, Goldstein said that Turntable has now reached over one million users — across platforms. Originally a web-only service, Turntable launched an iPhone app in September, which has helped increase the service’s reach dramatically.

Goldstein told former TechCrunch Editor Erick Schonfeld that part of the reason negotiations with record labels took so long is that it took awhile to work out how it would license music given the startup’s unique music listening configuration. The setup of Turntable’s listening rooms dictate a different experience for those DJing as compared to those who are just passively listening — apparently different licenses apply to both.

While the labels have plenty of clout over the young startup, it has become clear, as Erick points out, that the social music platform has the potential to be a significant marketing channel for the Big Four, with both the startup and the record labels partnering up to bring big-name artists to the platform — and to live events.

More on Erick’s interview with Seth here.

We’ll be updating as we learn more.