This is pretty much exactly how it happened with me, only much earlier on. When I was younger (about half of Peter’s age, in fact), I came across a keyboard that belonged to my sister in the midst of a bunch of older junk that was being given away. It had long since been given up, but I dusted it off and started messing around with it. Within a few minutes of figuring out the notes, I had taught myself the first song I ever learned on piano: Somewhere Over the Rainbow.
That’s not what Peter plays here, though. That’s the Super Mario Bros. theme written in my very rough hand-scripting. It’s interesting how everyone has their own unique style for writing notes, just as they have their own handwriting.
Also, the keyboard had an ability to speak the "Doe-ray-mee" notes in an awkward 1980’s digitized voice. The "Doe" sounded more like "Doo," so making it say "Doodie" was about the most hilarious thing my 6-year-old mind could process up to that point.