About Note Off (8cH nnH vvH) vs (9cH nnH 00H).
cH=Midi Channel, nnH=Note Number, vv=Velocity Value
In terms of midi protocol, they're still two completely different things.
From a practical point of view, most of Midi divices recognize them as Note Off.
In this case, the response - result, aurally is the same.
From a programming point of view, is completely different. Many newer midi devices, manage in different way these messages.
For example, some newer midi devices have the ability to sound a patch tone in different way, depending the Note Off velocity value. For example, you can trigger a second - different patch tone (sound) when the Note Off velocity value is over 50 e.t.c.
So, depending the receiver (midi device), you should consult his detailed Midi Implementation Chart.
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