06/2023
NiftyShifter
a through-zero, fullrange frequency shifter effect
stereo only - sorry. and built for 44.1kHz. (it will operate at higher rates, but filter out >20khz)
the range settings only affect the range of the GUI for better control in not-so-experimental use cases.
the "ultra high quality" mode doubles the steepness of the antialiasing filters to 96 db/oct and is normally only required for the higher range setting (10,000Hz), but you might want to check if it makes a difference depending on your input material.
nifty comes with a little testtone generator, which can teach you a bit on the topic of bandlimiting:
if you send a 20khz tone into a frequencyshifter which shifts for 20 kHz - while your samplingrate is 44.1kHz - the 20 Hz tone will be mirrored at 22kHz and hence end up at -4kHz. this is called aliasing, and we dont want to hear that shit.
on the lower end the problem is even worse.
the only option to get rid of that in an effects circuit (audio in, process, audio out) is to have filters before the effect, whose frequency follows the setting of the pitch shifter or frequency shifter in opposite direction.
Nifty is the base model of a series of shifters i made. to my knowlegde is was the first (and only?) FS for OS9.
in 2006 the algorithm had been upgraded to a better quality, which finally allowed these extreme settings of +- 20kHz.