pitchshifter

A pitchshifter is an audio effect or device that changes the pitch of an audio signal without significantly altering its duration. It can shift monophonic or polyphonic material by a user-specified interval, commonly expressed in semitones or cents. Many implementations also offer formant preservation to maintain natural vocal characteristics even when the pitch is altered.

Typical implementations fall into frequency-domain and time-domain categories. Phase vocoder methods analyze the signal in a spectrogram, shift the pitch by modifying frequency components, and then resynthesize the signal. Time-domain approaches include PSOLA (pitch Synchronous Overlap-Add) and granular synthesis, which manipulate short segments or grains to achieve pitch change with varying degrees of transient preservation. Modern pitch shifters may combine several techniques and may include formant correction to avoid unnatural vocal sounding results.

Common controls include pitch shift amount, often adjustable in semitones or cents, formant preservation or shift, dry/wet mix, stereo image, and, for real-time devices, latency and CPU usage. Many tools also provide automation, interpolation, and, in some cases, polyphonic processing for shifting complex chords or textures.

Applications span music production, live performance, and sound design. They are used for vocal harmonies, creative detuning and doubling, pitch correction, instrument transposition, and experimental effects. Hardware and software pitch shifters have evolved from early digital units to highly optimized plugins and real-time processors integrated into digital audio workstations, expanding the range of possible pitch-based workflows.