An instrument dating back many years, this was a very early an expressive electronic musical instrument with a ring and cord for pitch control, basic wave blending for the timbre plus a moving keyboard for vibrato.
Made in Japan, these new instruments are really beautifully made with custom metalwork and circuitry. You can buy them at a not insignificant, but quite reasonable €2,000 via ondomo.net - if you ask nicely, they might even add CV control too.
Complex arrangements with musical rules