This is a simple demo of the Web MIDI API. To use it, connect a MIDI device to your computer, and then play the notes as they appear on the staff.
If the note is played correctly, it will turn green. If the note is played incorrectly, it will turn red. When a noteOn event is detected, the command and note numbers will be displayed below the staff.
Live version of the sample app: https://jankleinert.com/getyournoteson/