joseph
“Will you jump up and down dancing and singing ”
You will be pleased to know that as people began singing on R”H I started yelling and throwing things.
It was abominable. right after unesaneh tokef they started singing some marching song they claimed it was a modzitser tune or something but they can’t fool me , you correctly pointed out singing ( certainly such a joyous upbeat tune) has no place on Rosh Hashana and is a modern innovation .
“and/or having a kumzits on Rosh Hashana”
I have been to some shuls (not my current one where all the tunes are upbeat and joyous as befits a King’s coronation) where they broke out in a kumzitz particularly during chamol