As you are thinking of tackling the problem it might be harder and maybe even near impossible without serious effort. I don't use spotify or straight windows media player (all about media player classic for me) but many programs like that will allow a measure of remapping their shortcuts instead. If they do not then perhaps something like
http://www.autohotkey.com/ will do it instead.
The proper audiophile crowd would probably crucify me for saying as such but I probably should also point out that often audio programs have a normalise command or an "album level audio" option which you can apply across a library- this will change the volume of all tracks to output the same and probably mean you only have to set the volume once.
Crazy alternative option- get a media playing device and wire it in through the line in of your computer.