In no instance of performance in any myth, legend, or fictional account has anyone ever had their ability to charm the audience, react to a change in pace, or intimidate their opponent prove the contest's deciding factor?
That, to me, is PERFORMANCE.
If you can play for hours on end as per the Endurance skill, that's great...but that ain't performance. Nobody ever went to a concert and was happy that the suckiest band played the longest.
That you choose the perfect song but play it poorly is not likely to win you a contest, unless it's one of those "that was bad but so sweet so you get brownie points for trying" things like winning the heart of a woman. It's
not going to win her soul back from the Devil.
Bluff? You can't bluff sweeps, slides, pinch harmonics, arpeggios, time signature changes, mid-song key changes for effect, hammer-ons, pull-offs or being able to play a progression of 1/64th notes (or faster)... And if the contest is close and goes to a "call & response" challenge to break the tie, if you don't have REAL skill, you can't fake it-
you will lose.
Even if it's not so dire as all that, PERFORMANCE is often the key...sometimes literally. There was an adventure on some animated kid's show back in the 1980's in which the locks in the city only responded to pure musical notes. What skill in 4Ed let's you ID something as the A# above middle C?