Just a suggestion:
There was a Ball, given by the Duchess of Richmond, a few days before the battle of Waterloo, attended by many of the higher-ranking officers in Wellington's army. In the final verse, might there be any ironic parallel intended between, on the one hand, a black mourning gown rather than a white wedding dress, and on the other the din of battle rather than the music of an orchestra?

"Who fell, 'mid an awful Ball-tune"

has little merit other than corresponding fairly closely to the line as noted by RVW, making some kind of awkward sense, and allowing that ironic contrast to be found.