What sets great musicians apart

I went to a San Francisco Scottish Fiddlers concert last weekend, featuring the great Alasdair Fraser who performed among 80 fiddlers and string players of mixed ages who filled up the stage of Lincoln Theatre.  Their collective sound was lively and impressive, though when (and only when) Alasdair played solo, I was transcended.  There was something about his playing-- and other great performing artists like him-- that set his music far above the usual "professional" performer's sound.  It got me thinking about why and how this happens, and I came to believe it could be a combination of things.  Of course there are endless hours of blood, sweat and tears of practicing on the instrument, out of sheer passion of just having to play... and there are elements of musical "talent" involved of having a super keen sense of pitch and embodying the rhythm, and as well the mature development of ear training and listening skills, but there is more.  I think this last essential element is what sets the great ones apart, and is captured in the saying that I've heard somewhere along my Dalcroze music and movement studies:  "Whatever you play, the first instrument is you."  It is the "you" part-- the inner self part-- that is developed so much in the truly great performers in addition to all of the other skills mentioned, that sets them apart from the rest.  Many possess a humble generosity of their spirit, and a loveliness and depth of their being that they express through their instruments...and the experience of being on the receiving end is, for me, what makes life so fulfilling.