I do it all the time for instance when playing chord sequences where some notes stay the same while others change.
Some synths seem to slightly detune the 2nd iteration so that the overlapping doesn't sound ugly, basically what you do with your octave stretching or whatever you call it.
In Sylenth that does not happen. I asked LD about it some time ago and he said I should very slightly modulate the pitch via velocity (which of course assumes one doesn't hit the same key repeatedly with exactly the same velocity).
Thinking about it, maybe we are talking about different things. In terms of Midi I think I understand what you mean. Basically the second note-on event for the same key should automatically be a note-off event for the previous note, right?
