Joe Hisaishi is a genius. He's the composer, and the pianist in this video. I'm a big fan of his music and I expect that you might be too, if you have a listen.
This composition, Kaze no Torimichi (Path of the Wind), is from Hisaishi's score for the Japanese animated movie, My Neighbour Totoro, directed by Hayao Miyazaki.
I hope that this video remains on YouTube for a while.