A string of note-ons following each other all for the
same pitch n without
any intervening note-offs for pitch n, IS PERFECTLY ACCEPTABLE provided
they are INTENTIONAL and NOT accidental.
No.
MIDI note-on represents a key press. Note-OFF - key release.
There is no logical way a key can be pressed a second time without first
releasing it.
It might be *technically* possible for a MIDI stream to contain two note-ons
(for the same key)...but it's SEMATICALLY incorrect to launch two voices
because you have no unambiguous way to turn just one instance off.
Back to your question.
a) Nothing, the note is already on.
b) Re-trigger, the voice is reset and the note gets played from the top.
c) Trigger, a new voice is assigned and will play simultaneously to previous
voices.
Given that it does happen accidentally. 'a' and 'b' are reasonable.
'c' is
wrong because with MIDI a key is either 'ON' or 'OFF', it can't be
'ON'
twice.
Anyone deliberately wanting the same key on twice must resort to using two
MIDI channels. Anyone wanting the same pitch twice must either resort to
multiple MIDI channels or to MIDI microtuning commands.
Best Regards,
Jeff