New phase-vocoder techniques for pitch-shifting, harmonizing and other exotic effects

Abstract

The phase-vocoder is usually presented as a high-quality solution for time-scale modification of signals, pitch-scale modifications usually being implemented as a combination of timescaling and sampling rate conversion. We present two new phase-vocoder-based techniques which allow direct manipulation of the signal in the frequency-domain, enabling such applications as pitch-shifting, chorusing, harmonizing, partial stretching and other exotic modifications which cannot be achieved by the standard time-scale sampling-rate conversion scheme. The new techniques are based on a very simple peak-detection stage, followed by a peak-shifting stage. The very simplest one allows for 50% overlap but restricts the precision of the modifications, while the most flexible techniques requires a more expensive 75% overlap.