My son, Jonathan (12) plays the piano. For a while we tried to assist his development by paying for piano lessons, but these only had limited success. He'd much rather work it out for himself. Yesterday I caught him playing Für Elise, which was a bit of a surprise, as his lack of enthusiasm for classical music comes close to mine. [It's a real difficulty in the ministry, as everyone thinks clergy are all into choirs, orchestras and the like, and talk to you as if you know what they are referring to. The nearest I get to classical is Genesis circa 1974]
Anyway, it turns out they were trying the tune out at school. Music was available, but Jono preferred to play it by ear in a scarily plausible way. He found it bewildering that some people couldn't even play it with the music. He then played it again, including a key change that I think may be lacking in the Beethoven* original.
Don't ask me where he gets it from.
* had to check on Wikipedia that I had remembered this correctly!