A Hilbert-Transformer Frequency Shifter for Audio
In contrast to conventional pitch-shifting effects which attempt to maintain harmonic relationships in the signal, a frequency shifter translates all the component frequencies of the input signal by an equal amount, disrupting the harmonic relationships and radically altering the sonic qualities of the signal. Ring modulation is a generalization of double-sideband suppressed-carrier modulation, and the frequency shifter is equivalent to a single-sideband modulator. Applications of the frequency shifter include the creation of bizarre distortions, phaser, and rotating speaker effects. An implementation is presented that is suitable for fixed-point digital hardware.