"Beatrice Harrison was a leading cellist of her generation, and friend of composers such as Delius and Elgar. She had the habit of playing her cello in the wooded garden of her cottage in Oxted, Surrey, near London. One evening in 1923 she was joined by a nightingale and was so enchanted by the sound that she persuaded Lord Reith, the director of the BBC at the time, to broadcast the cello-nightingale duet on live radio. Accordingly on May 19, 1924 the first ever live outdoor broadcast was arranged.
They interrupted the Savoy Orphean Saturday evening performance to go to Ms. Harrison playing Elgar, Dvorak, and the Londonderry Air ("Danny Boy"). No birds. The finally fifteen minutes before the end of the broadcast the nightingales started chirping.
On May 19, 1942, three years into the Second World War, the BBC was back in the same garden planning to broadcast the nightingales (sans cello). But 197 bombers, Wellingtons and Lancasters, began flying overhead on their way to raids in Mannheim and the engineer realized a live broadcast of this event would break security. The recording went ahead anyway since the lines to the BBC were open and a two-sided record was made, the first side with the departing planes, the second with their return (eleven fewer).
This recording is so poignant with the sound of the bombers behind the beauty of the bird song."