Browsing multiple Firefox files and controlling sound volume in each of them with Windows sound program.

Could there be index number for plugin devices when you are playing multiple browser files and using just one Flash Player plugin program ?

This would help choosing the particular sound to listen (and mix sound volumes by decreasing and increasing sound volumes) when you are browsing and playing multiple browser files at the same time.
 
Windows program (SndVol.exe) shows only one plugin device (Adobe Flash Player)and you can't easily control sound volumes from different files with that.