It's fine. But lucks simple expected features. Few examples, sheets scrolling and delay after pressing play button (also handler for pressing wrong key seems not working).
Anyway, good job.
The delay after pressing play button is baked in: after you play the first note the timer starts, not before. Not sure what yo mean by 'handler for pressing wrong key seems not working'? It turns the note red and logs a wrong note in the counters, did that not work for you?