Confirmation, finally!

Social music mixing site Turntable.fm announced Tuesday that it has closed a $7 million funding round led by Union Square Ventures.

Turntable, which had previously operated as Stickybits, also brought all of its existing investors into the round, including First Round Capital, Polaris Venture Partners, Lowercase Capital and Benchmark Capital. A few angels participated as well, including Troy Carter, Tim Kendall, Guy Oseary, Vivi Nevo and others.

Fred Wilson, principal of Union Square, will be taking a board seat at the new music startup.

Turntable.fm took off in the tech community at the start of the summer with one of those ideas that make you wonder what took so long for someone to make it a reality. In fact, they weren’t the first ones to create a platform for collaborating on a music mixing party, but they did it better than anybody else out there. Not only that, but they created a lot of hype by only allowing users in if they had Facebook friends already inside. Exclusivity begets excitement.

Though Turntable said today that its friend of friend network has grown to 60 million, or nearly 10 percent of the entire Facebook network, it also says that the requirement has been nixed. Now anybody can join the beta platform and play around with music mixing on the social Web.

Today, about three months since its launch, the service sees 600,000 people using the platform to socialize and share music with each other.

A couple days ago, Turntable launched its first mobile app on the iPhone, giving users the ability to be a DJ on the go. (Hopefully, no one’s DJing and driving...) Or, you can always just sit back and let the mixes play. The application is still in beta, so don’t expect it to work perfectly.

An Android version will likely be the next mobile release.