I'm afraid I was being a bit disrespectful, wasn't I! Although many of the songs were about love and the like, many also were relative impromptus in which (if it isn't too facile a point to make in the circumstances) the participants "took the piss" out of each other, or others well-known locally. Same principle as many other kinds of work-song, including shanties, of course.

On reflection I expect you're right about stored urine; any suspended solids (which would probably be the originators of potentially offensive odours) would settle out over time. How long was it actually stored for before use, though? Urine was widely used in the tanning and dyeing trades (as were dog faeces and oak bark, but that's a bit off-topic) and was commonly collected daily, though I can't remember if it was habitually matured before use.