Shostakovich’s Festive Overture marked the 30th anniversary of the 1917 Revolution with earnest fanfares and jolly tunes. 62 years on it smacks more of “Looney Tunes” and a cheesy kind of newsreel patriotism and you can’t help wondering if, behind all the laughter and frenetic flag-waving, the disillusionment had already set in. Mikhail Pletnev’s face suggested it had.