Fascinating stuff. Mastering is a black art. I never considered that beyond mastering for digital sound tracks which pretty much everything is now there is a whole new level of mastering for vinyl. The producers and masterers are the real geniuses behind the music. Its a proper black art. Your average track these days probably has between 10 to 20 individual vocal and instrument tracks on it unless its a basic rock, punk or blues track where it might be as few as five or even four but the more there are the more complex it is to produce, master and get right. Its mind blowing just how involved and complicated it all is.