Taking the piano example: after 1-2 years of progressive learning you can certainly give off the impression to somebody unfamiliar/untrained (including yourself to an extent) that you are actually quite good: Intermediate stage. But after awhile when confronted with more and more challenging stuff, by discovering different styles and finetuning your hearing; you at some point reach the very visceral and uncanny sensation of the countless possible roads you can now explore: advanced stage.
