Plot: BBC2 joins Radio 3 in stereo for the first half of tonight's concert of Russian music, live from the Royal Albert Hall. BBC Symphony Orchestra leader BELA DEKANY under its principal conductor Gennadi Rozhdestvensky play Rimsky-Korsakov's colourful Russian Easter Festival Overture and Victoria Postnikova is the soloist in the romantic Piano Concerto No 1 by Rachmaninov The concert also includes the first British performance of Cantus to the memory of Benjamin Britten by the Estonian composer Arvo Part Introduced by MICHAEL BERKELEY