When the BBC first started broadcasting, Music-Hall artists refused to appear: most of them went round the halls with one or two acts for a lifetime, and were obviously reluctant to 'give away' their material; and they were backed by the music-hall circuits' managements. Only slowly, after much negotiation, did it become possible for them to broadcast. Some broadcast in studios in front of an audience, but outside broadcasts from Music-Halls became a regular part of the BBC's output.
The technique arose of inserting the outside broadcast of a couple of acts - which of course had to fit in with the timing of the theatre concerned - into studio broadcasts. The problem with this was that while the outside broadcast was taking place, the studio audience - who could not hear it - were becoming restless and wandering about, causing difficulties when the broadcast returned to the studio.
The first suggestion made for coping with this was that the band - directed by Jack Hylton for these broadcasts - should continue to play for the studio audience alone. This was dropped in a hurry when it was pointed out that Hylton would want extra payment.
Then a revolutionary idea was presented. In a memo of 31 January 1929, Mr. Suttkey of Engineering Department suggested that a loudspeaker should be placed in the studio so that the audience could hear the outside broadcast (up to then there were no loudspeakers in studios). Objections that this might cause a howl-round (the sound of the loudspeaker being picked up by the microphone, returned to the loudspeaker, and so on, with increasingly noisy consequences) upon the return to the studio were countered by the invention of a relay-operated switch to mute the loudspeaker whenever any microphone in the studio was live (a circuit diagram was attached to the memo).
This device is so basic to broadcasting studios - it will be found in almost every cubicle-controlled studio in the world - that it is amazing that the BBC had managed without it for seven years.
After all that, another problem remained: the studio audience, being much smaller than the one in the theatre, sounded rather flat by comparison, which tended to kill the remaining acts for the listener; the idea of inserted outside broadcasts was abandoned and they were treated as separate programmes from the studio shows.