Having survived the elimination process that began over an hour before with the whittling away of hundreds of dancers, Billy and Tharbis reach the climactic showdown between them and legendary dancers George "Shorty" Snowden and Big Bea. Members of the equally legendary Harlem gang The Jolly Fellows, its members have inserted themselves into the surging crowd surrounding the dancers. The gang won't stop at anything to see their own win-- including slicing Billy and Tharbis with knives and razors as they dance pass them.
As the Gershwin's Liza (played by the Chick Webb Orchestra) segues into the magical and climatic ending of Duke Ellington's Harlem, why not have Tharbis, now bleeding profusely, spin out of the break-- throwing blood across the floor and the faces of the surging crowd-- stop, rise on her toes and, like an angel rising above the chaos of the dance floor, drop sand from her hands so she and Billy can dance in it; maybe in a mirrored soft shoe or tap routine; maybe something involving knee drops and slides that segue into dramatic modern dance where they roll in the sand, gather it up and let it fall over their supine, bloody bodies?
You can imagine this scene with the music below, starting at around 13:52. It opens with Ellington explaining how he wrote the symphonic piece as a tour of the great city, beginning at the southern end (110th St) and traveling up to 145th, sampling the city's life, sounds, and music.