I had recently presented several lecture-concerts in Singapore, looking at the History of Electronic Music in the 1st half of the 20thC.
Besides a quick breakdown of some of the prominent inventions, we took a look at the period in which the R&D took place, which happened to be during the 1st and 2nd world wars.
Naturally my good pal, Leon Theremin came up in my presentation, along with Maurice Martenot, who were neck and neck in getting their designs out.
Here is my post on LinkedIn : –
The race to design the 1st Electronic Musical Instrument : Theremin vs Martenot