OK, thanks Bavi - your images helped me find the actual midi data involved here.
Firstly, the octave numbering between Bavi's system and my data seems to be different. Bavi's data shows notes E4 and A3, in my data it seems to be E3 and A2.
That aside, I see what seems to be the same problems. Rather, oddities.
The location numbers are the midi tick counts in the raw data.
For the first case:
at 13680 I see a Note On for E3
almost immed there are damper events at 13681 and 13682
at 13696 I see another note On for E3
at the same tick there is a Note Off for E3
at 13707 there is another Note Off for E3
I suspect that this OUGHT to be a Note On between 13680 and 13707, but the Damper has caused a problem and a spurious On/Off in the middle.
I would guess that the On/Off would not be heard.
For the second case:
at 18886 there is a Note On for A2
18932 Note On for A2
18932 Note Off for A2
18960 Note Off for A2
No Damper events here, nothing else odd. The spurious On/Off is not explained.
Third case:
at 23729 there is a Note On for E3 velocity=47
at 23741 there is a Note On for E3 velocity=15 (which is unusually low ref other notes in the same area)
at 23741 there is an Off for E3, showing a velocity=0 (which is odd as the Note Off are explicit Off rather than Note On with Velocity=0)
at 23807 there is a Note Off for E3, velocity=65
Here, the second On is wierd, and the immed Off is also wierd.
In the first case, the Damper MIGHT have interfered with the data, but the pair of data On/Off was in fact there. The data I'm looking at does not show any missing events, it's just the order of the events that is messed up.
In all three cases, there is, in effect, a spurious On and an immed spurious Off, and in all three cases this spurious note might not be heard at all.
BUT, this depends on the playing hardware, and how the system would handle two notes the same sounding at the same time. As is suggested above, you cannot be sure that any system would see such cases as two separate notes, with overlapping On/Off, or would just end the note at the first Off and disregard the second Off as the note was not in fact On any more.
Geoff