The various use of the “Hup!” (or is it “Huh!”) fascinates me.
Sometimes it indicates a tune/ key change and other times it appears to be used to catch the person-playing-the-wrong-tune’s attention in order to glare at them.
And now and then it means “Speed Up”.
Sometimes it seems to be a general expression of appreciation that the tune/ set is “rocking inna groove t’ing, like a banging tune innit.”
You have to be quite confident to become a “Hupper” and the anarchic sessioneer could cause all sorts of mayhem with inappropriate Hupping.
You know you’ve arrived when you are a Hupper…