To get 20-20,000Hz we need a 1µF capacitor because C = 1/(2*π*10*20000) = 1/(2*π*10000*20) = ~0.8µF = ~1µF
I’m guessing it involves changing something with the capacitor.
I’d definitely be interested/able to build some sort of synth thing with a switchable oscillator, a filter. I certainly could do one with predefined fixed pitches.
What I would love to do which might be a bit more difficult would be to simplify the design of the Moog Etherwave theremin into something with more easily found components. I have found really good explanations of how the antennas work and the equations to find the different component values. It would require the use of some stuff that’s a bit out of the scope of this class but I’ve found that many parts of it are surprisingly really close to things we’re already doing.
I’d be really interested to learn more about the inner-workings of mic preamps and how different factors affect the quality of the sound.