I believe that each individual musician has some level of what they term "good" & "bad" music. I would call this their "standard"... the point at which something is judged by them.

Each music institution also has it's standard, and they teach it. The tradition is carried on & defended by their graduates.

Then there is the lay person/listener. They also have their standard of what is good & bad.

Every one of these standards vary, even if only slightly.

There is, in fact, no "standard" standard....Although institutionally trained musicians will tell us there is, and give a myriad of reasons, they are only perpetuating what they have been trained to do & what gives them legitimacy in their mind. Many musicians are encouraged to "play out of the box" as long as they do so from the box they are told to be in. The majority only rules because it says it does.

I contend that where music is concerned there is no "good" or "bad". There is only "different". Good & bad is only relevant when ego is involved. (it might be only the ego of protecting your standard)