The Frequency Shifter is a software effect for Microsoft Windows (VST) and Apple macOS (VST/AU) written in native C++ code. The main features are:
The Frequency Shifter shifts the spectrum of the input signal up or down along the frequency axis. This effect is also know as "Bode Frequency Shifting" or "Single Sideband Modulation"; IMHO one of the most underrated and ignored effects ever.
Do not confuse the Frequency Shifter with a pitch shifter! A pitch shifter multiplies all frequencies of the input signal by a constant factor while a frequency shifter adds (or subtracts) a constant amount of Hertz to (or from) those frequencies. Thus, the harmonic structure of the input signal will not be preserved in the modulated signal, resulting in a raw, inharmonic, metallic, you-name-it sound the more you apply the effect. Even more, if you mix a slightly shifted signal with the original input signal you will get some uncommon phasing sound.