There’s nothing unusual about Mr. Morris’s affinity for Baroque dance rhythms. And as his immensely appealing dancers move about in joyful order, you might not ascribe much significance at first to how some of them sink to the ground and have to be helped back up. But at the start of the adagio section, the entire cast is sprawled out — dead, sleeping or drugged — save for Sam Black, some Orpheus or Ulysses in the Underworld. With his assistance or without, the others might rise to their feet, but only to sink back down, wriggling… It remains unspecified what the titular article modifies, but if one thing is definite about this of-the-moment dance, it’s that Mr. Morris knows his Bach.