May I say I think we're going to get in trouble attempting to employ objective measures such as bell curves to a subjective subject, i.e. taste in music. For what's being suggested to be true about the bell curve being able to illuminate the nominal distribution of taste in music, that would imply and in fact require criteria transcendent of the people themselves whose taste in music is being judged in order to define just exactly what constitutes excellent taste, average taste, poor taste, etc., in the first place. Then, and only then could the bell curve be tested to see if it indeed applies to people's taste in music, per se, and conclusions be drawn from that, if any. Otherwise, I'm afraid we're putting the cart before the horse as far as bell curves are concerned. There is no criteria I am aware of that we could apply to a bell curve so as to enable the bell curve to be employed to illuminate something like the nominal distribution of taste in music, because we don't know what taste in music is, to begin with.
I think we can therefore more easily and properly just go with popular opinion over a sufficient period of time to null out the influence of mere fad or fetish, i.e., we can simply employ the test of time to decide what a masterpiece is, for example, including a musical masterpiece. This begs the question, how does one know what "good" music is, and what it ain't? Perhaps we can refer here to Louis Armstrong, who famously stated, "If you have to ask what jazz is, you'll never know".
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Then there is the example of music / literary / television critics, etc., who unabashedly pan artistic works based on their (self-proclaimed) good taste, only to see said works become wildly popular. Who is right? What does it mean to enjoy something?