Just discovered that Therevox has a new product, their Eurorack embodiment of the original Ondes Martenot oscillator, made modern. The Ondes VCO. I think this is a great idea.
https://therevox.com/ondes-vco/
It comes in your choice of four neutral colors.
ADDED : I’ve put a demonstration video that includes the Ondes VCO, over in this thread. The talking description starts at 6:07 of the video, and there is a simple sound introduction starting at 9:24. Note these oscillator circuits are different to the circuitry in the ET-5.