Harmonizer

A harmonizer is an electronic device or software that creates one or more harmony parts for an input audio signal by pitch-shifting copies of the signal and mixing them with the original. It is commonly used on vocals and instruments to add depth, build vocal choirs, or simulate multiple performers. The term originated with hardware pitch-shifting units in the 1970s and has since referred to a range of effects processors and software that produce harmonies.

Most harmonizers provide controls for key or scale, the intervals of the harmonies (for example major or minor third, perfect fifth, octave), the number of voices, and the dry/wet mix. Many modern units and plug-ins support polyphonic pitch shifting, allowing simultaneous shaping of multiple notes for chordal harmony. Formant correction is often included to preserve the natural character of voices, and some systems offer MIDI or tempo-sync features for musical alignment and live performance.

History and usage have evolved from early hardware devices, such as the pioneering pitch-shifter hardware of the 1970s, to contemporary multi-voice vocal processors and DAW plug-ins. Today, harmonizers appear in studio and live contexts as dedicated hardware units or software tools, integrated with vocal effects, guitar pedals, or keyboard setups. They are widely used across genres to produce lush vocal textures, create harmonized guitar parts, or simulate ensembles.

A harmonizer differs from a simple pitch shifter in that it intentionally generates additional pitched voices to form harmonies with the original signal, enabling vertical, chordal textures in performance and production.