Plot: BBC2 joins with Radio 3 -JL for the whole of tonight s Prom direct from the Royal Albert Hall. In each half, a concerto for two pianos, together with Russian music including a British Premiere of some rarities unearthed by Gennadi Rozhdestvensky , chief conductor of the BBC Symphony Orchestra leader BELA DEKANY Peter Frankl (piano) Tamas Vasary (piano) Part 1 Glinka Overture: Ruslan and Ludmilla; Dances from A Life for tne Tsar , Mozart Concerto in E flat, for two Pianos and orchestra (K 365) Introduced by Cormac Rigby