Today is the sixteenth of December and door sixteen is therefore now available to open on the BBC's official Doctor Who advent calendar. Behind the door is a previously unreleased music score written by Murray Gold. The score was used for U.N.I.T in The Sontaran Stratagem and is approximately one minute and four seconds long. You can listen to the track here on the BBC's official Doctor Who website. Three Doctor Who soundtracks for the new series and one soundtrack for Torchwood are also available for purchase and more information about them can be found here on Amazon.