Do you consider playing an instrument a form of concentration ?
Yes. Note, however, that there are different forms and levels of concentration when playing music on an instrument.
One possibility is to "read from sheet music". In essence such a concentration is not much better that copying a text on a typewriter.
Another extreme is to focus on the Final Sound, regardless if you play your own music or someone else's. People who can truly do it (such as Arthur Rubinstein and Ivo Pogorelich for example) create almost hypnotic atmosphere on their live concerts with audience experiencing shivers down their spines.
When you succeed in focusing on the Final Sound - all "technical" difficulties seem to disappear. It seems that Your Higher Self assists you in creating Beauty... After playing in such a state you wonder: "did I REALLY play this?"
Needless to say, there are many variations between these two extremes...
Tom,by focusing on the final sound, do you mean using your inner ear to play the piece in your head WHILE playing it out loud on the instrument, sort of synchronizing the two?
When you use your imagination to imagine the most beautiful sound, your consciousness seems to help you in achieving it.