Dance is arguably the most ephemeral of art forms, eternally of the moment and impossible to capture in its totality. From the late 19th century, it became possible to document it in photographs, and from the 20th century in film, but even footage of Rudolf Nureyev, Josephine Baker or Fred Astaire & Ginger Rogers in their pomp cannot quite render of power and brilliance that must have blazed forth from their every step when they danced live.