“The poetic core of Swan Lake is the act two pas de deux, that perfect lost-in-the-forest encounter in which Odette and Siegfried unfold the secrets of their hearts to the exquisite dialogue of Tchaikovsky’s cello and violin. It’s this duet that defines the tone of the entire stage, and establishes the audience’s relationship with it.”
But, it wasn’t. It never came into being at all. Ann Nugent explains:
“In 1870 he had occupied himself with large-scale ideas about writing a four-act ballet Cinderella, though he seems to have abandoned them fairly quickly, leaving no trace of any music he may have written for it.”
– Swan Lake, Barron’s Educational Series, Inc. 1985, p.14
Tchaikovsky, did, of course, later compose a mini version of the Cinderella story for the wedding scene in The Sleeping Beauty.