Sorry, the only thing that all "mastered" tracks have in common is that somebody claims it was "mastered". Don't get me wrong here. I think mastering is a critical part of the production process, but- one- the world is full of posturing incompetents who claim to be mastering engineers, and do not have the gear, the facilities, the ears, or most of all, the expertise, to do it. And secondly- multiple mastering engineers will take the same mix and treat it quite differently, including ones that really do know what they are doing. Third, many mixing and mastering engineers differ on what parts of the process each should be doing, so you will often find things the mixing engineer did that the mastering engineer would have liked to do- differently. To my ear, though, the key feature of a well mastered piece of music is that each of the parts sits in its own frequency space, as unecessary frequencies have been shelved, so each part can stand out without being loud.. A good master will always sound at least OK in mono, and of course, it will be in red book format. Is there an analyzer you can subject an object to that will tell you if it is art?-Richie