Hello, Katiedoo - The music for Cranko's
Onegin is indeed by Tchaikovsky, but was taken from a number of sources. Here's some information I found:
"Cranko’s first thought was to use music from Tchaikovsky’s opera Yevgeny Onegin, but Covent Garden and the Stuttgart Ballet both recoiled at the thought of turning an opera into a ballet. So his associate Karl-Heinz Stolze wove a score out of 'minor' Tchaikovsky. The act-one folk number is set to the 'Russian Dance' from the opera
Vakula the Blacksmith (a/k/a
The Slippers and The Caprices of Oksana); the party pieces of acts two and three — three waltzes (including a 5/8 number!), three polkas, a mazurka, and a polonaise — are drawn mostly from little-known piano works. The third-act pas de deux for Tatyana and her husband (here called Prince Gremin) is a pleasant bit of salon writing that improves in Stolze’s arrangement. The concluding pas de deux for Tatyana and Onegin is slyly drawn from
Francesca da Rimini, Tchaikovsky’s tone poem celebrating the lady from Canto V of Dante’s Inferno who did betray her husband."
From another source:
"Although Onegin is set to the music of Peter Ilyich Tchaikovsky, the renowned composer did not actually write the music for the ballet. Instead, the score is an amalgamation of Tchaikovsky compositions including
Composition for Piano,
Piano-Cycle Op.37,
The Seasons,
The Caprices of Oxana, and
Francesca da Rimini.
You can listen to some of these pieces (e.g.,
The Seasons) at
Tchaikovsky midi files. For the "lesser known piano pieces," you can try listening to all the piano pieces at this site and see if anything rings a bell.
I suppose you might try contacting the Boston Ballet or the National Ballet of Canada and asking which specific pieces are used.
Good luck!