I think I need this because I listen over headphones to audio that changes volume levels (eg. Spotify playlists with a variety of artists) in a somewhat noisy office environment (I can't just listen more carefully when the music is quiet) but don't want to turn the volume up too high. I also don't want to have to be constantly reaching for a volume slider. Currently, I am constantly reaching for a volume slider, because some song comes on that's loud and I have to turn it down, then a quiet song comes on and I forget to turn it back up, and eventually I notice I'm distractedly listening to conversations from sales instead of focusing on my tasks and drowning them out with background music. And heaven help you if you have a source of audio with ads (eg. Pandora or Youtube playlists), where every half hour you'll get your eardrums blown out with some obnoxiously loud ad break.

My uneducated expectation is that this would run in the background on my Linux laptop, letting the volume decay in between beats and as the song switches, but amplifying quiet songs and compressing loud ones. It would be nice if some of the dynamic range of a song was preserved, but instead all songs should go from, to use the musical terms, mezzo-pianno to mezzo-forte. I don't particularly care if it has to buffer the next 10 seconds of the song to make that work, but as I like to stream a variety I can't wait for it to compress a full hour of audio.

Is that what this does? Do I need to use mpv, or have a local/offline mp3? Is there a better way to do what I want?