Not sure your definition of "original" here. Analog synths were experimented with since the 1920's and 1930's[1] with digital synthesis arriving around the early 1970's[2].

The Electronium was late enough not to qualify as an "original" synthesizer, unless you mean it was "all original" work by Scott, which I'm not sure is completely true either. With the first working unit developed only by 1969[3] and used at Motown throughout the 70's, I thought that it was worth differentiating from the digital synthesizers which really arrived not that much later.

[1] https://en.wikipedia.org/wiki/Analog_synthesizer

[2] https://en.wikipedia.org/wiki/Digital_synthesizer

[3] https://en.wikipedia.org/wiki/Electronium