Original design
1st rough concept
2nd rough concept
I've been frequently using media control ever since I upgraded to W10. I assigned play/pause to one of the macro buttons of my mouse. Spotify is nearly always on, when I want to watch something I don't go back to Spotify app, I just simply click one button and it stops and sometimes I also use the media overlay to adjust the volume. But you see, it affects the whole system wide volume. So having a seperate volume bar for the current media player would be something that would benefit me. I'm more towards the second design in which he volume bar on the left controls speaker volume and the one on the right controls only the application being played.
I'm already using EarTrumpet but I'd prefer something more like the media overlay for convenience.
Btw if you know a mod/tweak that can do this please inform me. I'm all about that tweaking/modding life.