pitchchanging

Pitchchanging is the process of altering the perceived pitch of an audio signal by changing its frequency content. It is used in music production, sound design, and speech processing to raise or lower pitch without or with varying degrees of tempo change. Pitch shifting typically preserves the duration of the sound, while more general pitch adjustments may accompany time-stretching to alter tempo as well.

Common methods include frequency-domain approaches such as phase vocoders, and time-domain techniques such as PSOLA and granular synthesis. Phase vocoding analyzes spectral components and recombines them at a shifted pitch, while PSOLA works in the time domain by overlapping and adding pitched segments. Granular methods manipulate small grains to achieve flexible pitch changes. Formant preservation is often a goal in vocal processing to avoid an unnaturally hollow or shrill result.

Applications include vocal tuning and harmonization, instrument transposition, and creative effects in music and film sound. In software, dedicated pitch shifters or auto-tune tools allow real-time or offline processing. Pitchchanging is also used in linguistic research for pitch manipulation in speech stimuli, and in synthesis for character voice design.

Challenges include audible artifacts such as phasiness, graininess, or formant distortion, especially with large pitch shifts. Real-time processing requires low latency and efficient algorithms. The choice of method depends on the source material, required quality, and whether formants must be preserved.

Historically, early digital pitch shifting appeared in the late 20th century with resampling and resynthesis techniques, followed by more sophisticated phase vocoders and PSOLA-based tools. Modern software provides high-quality, real-time pitchchanging with adjustable formant preservation and various algorithms.