Uwe Schüler from the Kulturgüterschuppen in Dusslingen has designed an easy-to-solder Thermin for small budgets. It is based on the CMOS 555 chip and sounds very good for components around 15.-€. It was designed for a workshop at Zirkus (JKU Linz) as a project of "Vom Hören und Staunen: Akustik trifft Physik"
More info: https://dorninger.servus.at/workshop-vom-h%C3%B6ren-und-staunen-wir-l%C3%B6ten-ein-theremin
drkmbnt "Jammin' with the CMOS-555 Theremin" from Wolfgang Dorninger on Vimeo.