<p>Every MIDI note consists of two messages, a NoteOn and a NoteOff message. Each one has a note number and a channel (also a velocity, but that isn't relevant here). The MIDI standard stresses that it is invalid to send a second NoteOn for the same note number on the same channel before a NoteOff for the first NoteOn. It is more or less impossible to do this with a physical MIDI controller such as a keyboard, but remarkably easy to trigger when editing in a DAW - simply overlapping two instances of the same note will do it.</p>
<p>Ardour offers many options for how to deal with instances where you overlap two instances of the same note. Which one to use is a per-session property and can be modified from <code>Session > Properties > Misc > MIDI Options</code></p>
<dlclass="wide-table">
<dt>never allow them</dt>
<dd>Edits that would create note overlaps are not allowed</dd>
<dt>don't do anything in particular</dt>
<dd>Ardour leaves overlapping notes alone - the behaviour of a MIDI receiver (plugin or hardware) is undefined</dd>
<dt>replace any overlapped existing note</dt>
<dd>When one note is moved to overlap another, remove the one that wasn't being moved</dd>
<dt>shorten the overlapped existing note</dt>
<dd>When one note is moved to overlap another, shorten the one that wasn't moved so that there is no overlap</dd>
<dt>shorten the overlapping new note</dt>
<dd>When one note is moved to overlap another, shorten the one that was moved so that there is no overlap</dd>
<dt>replace both overlapping notes with a single note</dt>
<dd>When one note is moved to overlap another, merge them both to form one (longer) note</dd>
</dl>
<p>Changing the option in use will <strong>not</strong> retroactively make changes - it will only affect new note overlaps created while the option remains chosen.</p>
<blockquote><p>Ardour does not check for note overlaps across tracks or even across regions. If you create these, it is your responsibility to deal with the consequences.
