Recently, the question of the best sequence of scenes in which to perform the opera has gained some prominence. Borodin did not complete a libretto before composing the music to "Prince Igor". The opera has traditionally been performed in the edition made by Rimsky-Korsakov and Glazunov. It will be obvious that the positions to which they assigned the Prologue, Act 3, and Act 4 cannot be changed if the story is to make sense. However, because the events of Act 1 and Act 2 overlap and are independent of one another, Act 2 may just as well precede Act 1 without any loss of coherence. Soviet musicologists Pavel Lamm and Arnold Sokhor reported the existence of a written plan (now in Glinka's Musical Culture Museum, Moscow), in Borodin's hand, that specified this sequence of scenes: