Steven,
It's beautiful!
I'm very critical of paintings of musicians and I think you've captured something really special in this one.
I have a project going at the moment where I am painting different musicians whom I admire (with their chosen instrument and with heavy focus on their hands), using composition and colour to recreate the sounds and tones of the instruments. (in square format) So far I have done the flautist, the cellist and the pianist. I have a way to go yet. Big challenge!!
With regard to your use of your camera as a way to check the image, I will use every trick I can think of to catch out any errors. Camera, mirror, bells, whistles, friends, relatives.
I recently painted a 6m x 3m backdrop of the inside of a cathedral for a photographer. Very proud of it I was until she gave me a proof (fortunately) of a sample photo and guess who had a BIG!!! mistake in the perspective of a little wall off to one side. It went down where it should have gone up but in life, I couldn't get far enough back or hang it high enough to compare it to the other lines. Embarrassing? Fixable!!!!