I am trying to understand the numbering of Borodin's Polovtsian Dances, from Prince Igor. They seem to be performed as an undivided group (lasting about twelve minutes) yet the first dance is No. 8? Wikipedia suggests there are two dances, numbered 8 and 17. Can anyone explain this?
Basically, the dances are separated into two main groups in the opera. The first dance is No. 8, and the remaining dances are found in No. 17.
By these "numbers" we quite literally mean that they're numbered this way in the full opera score; it's a practice called number opera. So numbers 8 and 17 don't apply to the dances at all, just to their overall placement in the full "Prince Igor" opera.