WindFlyer, on Oct 31 2006, 01:58 PM, said:
For the 1895 Petipa setting, a fair amount of the original partiture was re-ordered, some music was cut, and some was added. Tchaikovsky was already dead, so the music that was added, while composed by Tchaikovsky, was orchestrated by Riccardo Drigo (an in-house composer at the Mariinksy Theatre at the time). The music came from a set of 18 Piano Pieces published as op. 72. The following three pieces were added: No. 11 (Valse bluette), the corps piece inserted early into Act IV; No. 15 (Un poco di Chopin), inserted toward the end of Act IV between the beginning and closing of the Scene finale of the original partiture; and No. 12 (L'Espiègle), inserted into the Black Swan pdd before the Coda.
I do not recall having ever heard these 'Drigo' pieces performed by companies other than the Mariinsky–though they may have.
The current Royal Ballet production, staged by Anthony Dowell, includes these Drigo-orchestrated pieces in the fourth act. Dowell staged the production with the consultation of scholar Roland John Wiley (who's book, Tchaikovsky's Ballets, is very detailed and informative) - and this production is considered to be one of the most musically close to the 1895 production. It includes, in Act 1, the switch of the pas de trois to occur before the waltz and these interpolated piano pieces in Act IV.