"The Entertainer" was a tune once played by Missy on the piano, while visited by the Twelfth Doctor and Bill, in her vault. (TV: The Lie of the Land)
In 1977, an ill-fated hiker whistled this tune in the woods near Fetch Priory, before his untimely demise. (TV: Image of the Fendahl)
Behind the scenes
While this piece goes unnamed in both stories, it is easily recognisable as the 1902 ragtime two-step by Scott Joplin.