Ridcully tapped the nozzles.
Nothing happened. He looked at the controls again, and realized that he’d never pulled the little brass lever marked ‘Organ Interlock`.
He did so. This did not cause a torrent of pleasant bathtime accompaniment, however. There was merely a thud and a distant gurgling which grew in volume.
He gave up, and went back to soaping his chest.
‘——running of the deer, the playing of… huh? What—’
Later that day he had the bathroom nailed up again and a notice placed on the door, on which was written:
‘Not to be used in any circumstances. This is IMPORTANT.’
However, when Modo nailed the door up he didn’t hammer the nails in all the way but left just a bit sticking up so that his pliers would grip later on, when he was told to remove them. He never presumed and he never complained, he just had a good working knowledge of the wizardly mind. They never did find the soap.
Terry Pratchett, Hogfather