Most often, the stories we hear about confidence are the ones where the athlete (or musician) was certain that success would be theirs. Where they went to the Olympics (or the big audition for principal trombone) absolutely convinced that they were going to win.
That kind of confidence is nice, and it can definitely be an asset in tough high-pressure situations.
I recently had the good fortune of hearing an Israeli conductor by the name of Itay Talgam give a talk on leadership.
There is, undoubtedly, a certain standard of excellence that must be upheld. A command of the mechanics of playing one’s instrument. A deep and nuanced understanding of the vocabulary, grammar, and language of music.