If you look in the upper right corner, there's a "MIDI Select Device" button.

I think there's also a lot to be said about having a real score in front of you. I used to sight-read for a living (guitarist on cruise ships) and thought that the first grok of the visual where you take in the form was more important than the up/down of a melody.

By the way, this guy is a monster sight-reader: https://www.youtube.com/watch?v=JZMroQOtS_U

Before clicking the link I already knew you were referring to Tom Brier :)

That is quite humbling. He is obviously a very skilled musician and can play ragtime like Scott Joplin but picking up a new piece and playing it by sight without any mistakes that I could see or hear, is amazing.

Yes, practicing piano by playing a piano is probably the best approach

On chrome this works with midi keyboards.

I'm missing the pitch too. (Edit: ah you're supposed to connect it to a MIDI device, but who owns that/how does that cater to mobile users). What good is it knowing the note is C5 without knowing what C5 sounds like, in other words I'd be able to identify the notes but I wouldn't know what the song sounds like...