I enjoy the song too ~~~~~~~~~~~

The argument is if Lang knew what he was playing before.

It is quite obvious he knows.  Even a kid pianist, before he learns a song, a good teacher would explain to him what he was playing, and trying to have him understand the music and its background.

As a concert pianist, Lang said he didn't know anything about the song he was going to play, only because it sounds right, who would believe him?!