Checks whether the status type of the message is 'Note On'
_and the velocity value is actually greater than zero_.
IMPORTANT: As per MIDI 1.0, a 'Note On' event with a velocity
of zero should be treated like a 'Note Off' event.
Which is why this function checks velocity > 0.
Checks whether the status type of the message is 'Note On' _and the velocity value is actually greater than zero_.
IMPORTANT: As per MIDI 1.0, a 'Note On' event with a velocity of zero should be treated like a 'Note Off' event. Which is why this function checks velocity > 0.