Sorry, this article is still being revised.

However, the gist of it is that:

(a) Dance and jazz bands in the U.K. and the U.S.A. used virtually the same standard pitch. Ours was A=439 Hz, while the U.S. used A=440 Hz. The difference is negligible.

(b) Dance and jazz bands, with their trumpets and saxophones mostly based on the keys of B flat and E flat, tended to use a specific range of keys. G, C, F, B flat, E flat and A flat. D flat was only very occasionally used; likewise A. Other keys were very scarce.

(c) Publishers stock arrangements were widely used, and these definitely tended to use the range of keys given above, otherwise their stocks would have been difficult to play – and they would not have sold well! Bear in mind that for every band that made records in the 1920s onwards, there were scores if not hundreds of semi-professional bands buying these stocks. Their skills were, of course, generally less than the star recording bands.

(d) For variety, publishers’ stocks would often change the key during the score, usually by short bridge passages. The intervals employed were rather predictable:
(i) Up the natural ‘ladder’ of keys; e.g. From C to F to B flat.
(ii) Up a tone; e.g. from B flat to C; F to G and so on. (Seldom if ever   did they go a tone down!)
(iii) Up – and down – a minor third. There are many pop songs of the 20s & 30s that do this within their chorus. The Gershwin brothers’ ‘S’wonderful’ is a good example; it changes from E flat to G in the middle 8 (release), returning to E flat for the last 8 bars. There are many other E flat/G songs, but few that go from F to A flat, like ‘China Boy’. Don’t ask me why!

If you have a well-tuned piano in the room, check out the key of a dance band or jazz 78. If it comes out in, say, B major, it’s 99% certain to be wrong; it should be in either B flat or C, so adjust your turntable speed & check it out in those keys; ‘sharp’ keys like B, E, A & D were not ‘preferred keys’ for dance & jazz bands.

If you find a dance band playing in E major, it probably should be E flat or F, and so on.

You may find that when you speed up your turntable, the performance might begin to sound slightly ‘Mickey Mouse’; this is, of course, evidence that the true key is a tone lower.

If you don’t have a piano or keyboard, many of the better type of ‘toy’ keyboards are digital these days, and provide a very accurate pitch.

More here later….