Plot: BBC2 joins Radio 3 in stereo for a live relay of the first half of this evening's Henry Wood Promenade Concert from the Royal Albert Hall , London. Mozart Symphony No 41 in C major (Jupiter) (K 551) Mozart Flute Concerto in G major (K 313) Debussy Syrinx James Galway (flute) BBC Scottish Symphony Orchestra leader RAYMOND OVENS conductor Karl Anton Rickenbacher Introduced by CORMAC RIGBY Sound GRAHAM HAINES , JOHN MCCULLOCW Lighting TOMMY THOMAS Directed by RON ISTED For the best effect viewers with stereo Radio 3 should turn off TV sound and position their speakers on either side of the screen, but a few feet away