This is called the David Tennant Treat 4 Today but I'm not sure that 'Treat' is really the correct word today!
This is a song called David Tennant's Hands which has been posted to Spotify. (You do not have to subscribe to Spotify to hear it.)
The organist (and singer I assume) is Christopher Bowes.
Click here to listen to it.
Tomorrow we will revert to a proper 'Treat!'