Rewatching scenes on YouTube, I'm making observations about Bill at the piano. First, he's playing the song from memory -- he didn't reopen the sheet music after closing it on Frank. Second, he's not playing the exact same thing Frank did -- he's at a slower tempo, changing the arrangement to accommodate that, but also in a different key. He must have made those changes to the song himself, and done them often enough that he could remember it all. Or possibly he's just such a skilled pianist that he could improvise the correct chords underneath his voice. Either way, he's clearly a music lover. And the fact that Frank immediately figured him out and rifled through his music to find that exact song that he knew well enough to passionately play his own version from memory is just. *chef's kiss*