Music Composers Unite!
for guitar, its all about facial expressions! :D
I believe its the ability to be inside of, and actually be part of the music, as opposed to being outside of it, and simply performing or playing the notes..
A kind of merging and being one with the music, and letting it play you...
I definitely subscribe to Bobs comment as I've had that feeling many times when performing. Hard to describe, but it feels like you're not actually you doing it, more like your channelling energy or a force. Sort of an auto-pilot sensation where your normal characteristics and mannerisms have been put in a limbo or trance-like state allowing this connection to happen. I think it has alot to do with the intent of the musician, their state of mind and also how the piece affects them. A very interesting subject!
It's a good question.
You could superficially address it by posing a hypothesis.
If we imagine a blind test, using only a recording (no live performance), if one was generally found to be the preferred performance, then we would have to conclude that there is something different about the way the preferred one is played.
Alternatively, if we did the same test and our results were that there was generally no great preference, and yet we knew that in a live performance one of the performers was preferred, then we would have to conclude it had something to do with their stage presence.
From this little thought experiment, it seems that the pivotal factors are the subtleties of the delivery and/or the performer's stage presence.
Perhaps additionally, I think it's possible that people amassed in an audience will, if only to a minor extent, succumb to "mob behavior," thereby occasionally (or habitually) cheering a performance which has no great virtue over another one.
Aaron Marshall said:
"You can be at any technical level, but you have to feel."
In addition to what Chris said, I'd add that I cannot remember seeing a performer utilising extremely good technique and not "feeling" what they are doing.
It certainly works the other way around - that is, you can have someone with limited technique perform beautifully. A good performance might be constituted by all sorts of things, not just technique.
But I don't know about having excellent technique and not performing with "feeling," beauty, power and all the rest of it... because these things precede technical development: If you're not a beautiful performer, in all likelihood you're not going to have the staying power (or the opportunity) to develop a good technique in the first place... that is, people who are technically versatile have already proven themselves at lower rungs of the ladder. Put it this way: how many champion tennis players are there who are entirely without passion when they play?