This extension is really satisfactory for audio and pitch speed changes, whether you decide to alter the tone or not while increasing the speed, the only exception is that when you only increase the pitch, it is barely audible and does with the current one instead of editing exactly that. Otherwise, it works well

works almost perfectly but it stops youtubes built in speedup from working

Un petit problème à signaler, avec les raccourcis clavier + et -, la tonalité change, mais aussi le tempo :-/
Sinon, ça marche plutôt bien

A great Firefox alternative to the Chrome-only https://transpose.video, which does what it says on the box.

The pitch-shifting algorithm does produce slight artifacting at certain pitches, but overall works well enough to be able to sing along.

*However, keep in mind that for it to work well, the (preserved pitch) option has to be turned off.