Are you folks sure anything is being generated on the fly here? I get a pre-generated version that is exactly the same every time I load the page.

I'd like to see some sort of explanation of how the neural network knew how to produce unique chord progressions pleasing to human ears, even adapting the lead to fit these new chords, for a song that contains none of those chord progressions. What is the other unrelated music it used as learning material for this?

I'd ask OP to fill us in, since it's his site; but it seems he perhaps prefers not to waste his time translating back and forth to English, considering his historical lack of comments on HN. Oh well.

Aha, figured it out. When you switch away from the tab, Chrome reduces the play speed, which is why it sounded different and like slowly banged out minor chords.