Pitchshiftelés

Pitchshiftelés is the process of changing the pitch of an audio signal without (or with minimal) alteration of its duration. It is used to raise or lower tones in music, vocal processing, sound design, and related fields, often with the goal of preserving natural timing while altering pitch. In some cases duration is allowed to change slightly if the method emphasizes different musical effects.

Two broad classes of algorithms are commonly employed. Frequency-domain methods, such as phase vocoder approaches, analyze short segments of the signal with a Fourier transform, shift the pitch by resampling the spectral content, and then resynthesize the signal. Time-domain methods, including PSOLA (Pitch-Synchronous Overlap-Add) and related segment-based techniques, manipulate individual pitch periods or short audio segments to achieve the shift, typically offering lower latency and better handling of transients. Modern implementations may combine techniques or include formant preservation to reduce unnatural vocal timbre during large shifts.

Applications include pitch correction, creating harmonies, character or effect design for vocals and instruments, and sound restoration tasks. Real-time pitch shifting requires attention to latency, CPU usage, and potential artifacts, while offline processing can produce higher-quality results. A common challenge is avoiding artifacts such as transient smearing, phasing, or a metallic timbre, especially at extreme shifts. Formant-preserving methods aim to keep vowel qualities stable while changing pitch, contributing to more natural-sounding results for voice, though they may introduce their own trade-offs in timbre accuracy.

Overall, pitchshiftelés is a versatile tool in audio production, enabling creative and corrective pitch manipulation across a range of contexts.