My son Dan, who is now a music major in college, spent a lot of time playing along with CDs when he was 10 or 11 years old. In this way he taught himself how to play the Irish button accordion.
I sketched him in one evening amid the clutter of my painting studio. I enjoy this kind of unstudied natural situation, where someone is just doing what they love to do, without consciously posing.
My main concern was how to simplify the scene so that I had only two principalities of tone. Using 2B and 4B graphite pencils, I rendered his accordion and his hair as fairly uninterrupted dark shapes, which helped to bring out the light shape of his left arm.
Dan Gurney, link.