Mrs Widgery's Lodger
An old morris-dancing tune that echoes across time and space with many strange repercussions.
The Lancre Morris Men dance this tune as part of their repertoire and it is exceedingly effective as the soundtrack for killing Elves.
In Ankh-Morpork, an Order of Wizards is known as Mrs Widgery's Lodgers after Unseen University's first student landlady.
When Kin Arad and her team discover the other Discworld in Strata, to prove that Silver is no threat to the Vikings, Kin Arad gets her to act as a tame dancing bear, whistling the tune of "Mrs Widgery's Lodger" for the Shand to dance to.