This is a Discworld folk tune which is referenced twice in the canon. It is referred to in Pyramids as a basic tune for dulcimer learners, which is expected to be part of the simple repertoire any half-competent handmaiden or concubine should be able to perform to ease and soothe her master's soul after he's had a hard day ruling and needs to unwind. Ptraci is still unable to master its subtleties after quite a few years of trying, although Pteppicymon XXVII will still select her to play for him, on the grounds that her technical ineptitude makes him feel better by comparison. The tune re-appears in Soul Music, as part of Blert Wheedown's primer of simple tunes for guitar learners. Crash, from Insanity, discovers it's the only tune he can even halfway play, and doggedly sticks to it despite whatever the rest of Ande Supporting Bandes are trying to perform, generally Anarchy in Ankh-Morpork.