"Hark the Herald Angels Sing" was a Christmas song.
When the Second Doctor and Jamie McCrimmon were imprisoned in Trenton with time travellers Stephanie and Edward, they heard their Hessian guards singing "Hark the Herald Angels Sing" in German. (PROSE: The Revolutionaries)
In the year 5343, a choir from a human colony on Mendorax Dellora sang "Hark the Herald Angels Sing". (TV: The Husbands of River Song)
