"The Holly and the Ivy"
From Tardis Wiki, the free Doctor Who reference
"The Holly and the Ivy" was a Christmas carol. When the Second Doctor played "Silent Night" on his recorder, Victoria Waterfield guessed he was playing "The Holly and the Ivy". (PROSE: Saint Nicholas's Bones)
It was sung by a group of humans, including Sarah Jane Smith, who had inadvertently been captured by a Hazoodian ship. (PROSE: Autaia Pipipi Pia)