I Can't Decide

"I Can't Decide" was s song of which The Master was fond. He requested it to be played during his command of the Valiant during the Toclafane invasion, and sung it while taunting the aged Tenth Doctor. (DW: Last of the Time Lords)

As made clear in the episode commentaries and Doctor Who Confidential, the song was originated by The Scissor Sisters on their album Tah-Dah.