How to Raise or Lower the Pitch of a Voice?

The Problem

You have a voice audio recording and you want to make it sound higher or lower. You need to match a different key or correct intonation.

Resampling the entire signal, a naive approach, will change the pitch, but so does the speed. Raise it and you get chipmunks. Lower it and you get an underwater effect.

So, how do you change the pitch while preserving everything else about the voice?

Quick Answer

Use an OverLap-Add (OLA) method to split the audio into frames.
Resample each frame to the target pitch, then recombine to restore the original duration.

The basics are there, but it requires quite a lot of care and a bit of AI squeezed at the proper joints to be done properly.

How you do it with Pitchmeld

1import soundfile as sf

2import pitchmeld as pm

3audio, sr = sf.read("input.wav")

4shifted = pm.transform(audio, sr, psf=2)

5sf.write("output.wav", shifted, sr)

The psf parameter is the pitch scaling factor (see doc):

1.5 raises by a ~fifth
2 raises by one octave.
0.5 lowers by one octave

Audio Examples

Below are examples of pitch scaling applied to both sung and spoken recordings. The original duration is preserved.

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If you want to know more, have a look at the post about transfo