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"600% Sound Volume" Firefox add-on blocked after apparently committing affiliate manipulation
(addons.mozilla.org)
I could not find any articles with further information on the topic.
There seems to be a fork with tracking removed, but it only has about 2000 downloads, so proceed with caution.
You can set the volume by tab and not only globally for the browser. It's also very useful if a website doesn't have volume controls. And if the audio is too quiet, you can amplify it (as the name says) to up to 600%.