I took some lessons as a kid but trained myself by ear. I did it the way jazz musicians used to learn years ago, which is to play records and slow them down to figure out the notes. At first I tried to imitate Red Garland, who was my favorite jazz pianist.
My writing is really intuitive. As a kid, I went to school in New Jersey and hung out in New York, so the way kids used to talk got into our earlier songs.