The ondes Martenot (which is French for “Martenot waves”, also known as the ondium Martenot, Martenot and ondes musicales) is one of the first electronic musical instruments ever created. It was invented in 1928 by Maurice Martenot and it’s sound was very similar to a theremin – except with much more control over the timbre of the sound.
I’d stop short of calling it a real synthesizer, but it did have switches to control the sound. It even came with 4 very different speakers that could be switched on …

I remember a very long time ago when I owned a TRS-80 color computer with 4k (!) of RAM made by Radio Shack and I bought the synthesizer cartridge for it.  It was so much fun just tweaking the filter and other parameters.

 Delia Derbyshire is the composer of the original theme music to the cult favorite TV show Dr. Who. She worked for the BBC’s Radiophonic Workshop in 1963 and was asked to record the theme written by a composer named Ron Grainer. She turned this composition into a ground breaking (at the time) electronic masterpiece.