Benesh.

Dance With my oh so sudden, Bussell inspired interest in ballet, it dawned on me that for all the talk in those BBC Four documentaries about how the choreography for these productions have been passed down across the centuries in a kind of movement based version of oral history, movement history I suppose, that in the case of historic reconstructions, there would need to be some kind of record of the original moves ripe for interpretation.

Sure enough, this exceeding thorough 2011 article from Ballet News fills in the blanks, explaining that such persons as notators or choreologists work as a kind of dance stenographers during rehearsals, creating a visual record on musical paper using special notation (Benesh notation) that "remembers" the shape of scenes, the shapes of dancers within those scenes and the general sense of how a work should be constructed running along with the music.

Within the interview with one of the choreologists, there's a strand about how in some cases dancers haven't been taught the notation and end up relying on video records of previous performances, but how this is an imperfect approach because it could mean that the given dancer is attempting to recreate an imperfect performance.  If the original practitioner had a stiff back or something else which inhibited their interpretation of the dance, that can then, unfortunately be replicated.

This also explained to me how, as I'd heard elsewhere ballets can be lost just as unfortunately as plays or films.  If there's only a single manuscript of the choreography in existence, as was sometimes the case in dance companies in which there was a single choreography working from their own copy, it's near impossible for the dancers themselves to produce a version from memory.  Unlike a play, they may not necessarily be completely aware of the movements of others.