Normalise audio volumes

[OMGDuke]

Some songs are louder/quieter than others. Look into audio normalisation.

https://developer.mozilla.org/en-US/docs/Web/API/DynamicsCompressorNode

Something like the Audio compression in the FFZ chrome plugin for twitch

[GMP672]

If I may suggest something: Audio compression would impact how the music sounds.
Better approach would be to utilize Youtube Loudness Standard and apply static +- dB (or volume slider percentage) based on Content Loudness measure.

However, as far as I looked into it, its calculated by the player, not by Youtube itself.

I have not found a good way to retrieve that data yet (e.g. https://stackoverflow.com/questions/46819958/extract-youtube-stats-for-nerds-through-an-api)