Arduino's ADC are limited to 10 bits (1024 values maximum). Full-resolution midi is available on some controllers and will give you generally 10 useful bits of precision. The possible resolution in standard hi-res MIDI is 14 bits, but there are often only 10 useful bit because the underlying ADC is limited to 10 bits. In any case, you might want to experiment with different approaches, different ways of scaling your values (log scale, etc.) Another approach if you don't have a hi-res midi controller is to use 2 knobs: coarse & fine. J-F

The Teensy 3 has 13 bits of resolution for it's ADC and can be programmed to act as a usb midi controller quite easily. Another possibility could be to use a controller with an encoder in relative/increment mode which allows more precision.

Thanks for the responses all!

highest resolution ... when it is ... big? theremin -> arduino -> max?