manual/include/create-midi-regions.html

<p>
  Although recording MIDI is a common way to create new MIDI regions, it is
  often desirable to do so as part of editing/arranging.
</p>
<p>
  To create a new MIDI region, simply <kbd class="mouse">Left</kbd>-click in
  a MIDI track. A region will be created that is one bar long. You can
  <a href="@@trimming-regions">trim</a> it to any
  length you want.
</p>
<p>
  Once you have created a region, you will probably want to
  <a href="@@add-new-notes">Add some notes to it</a>.
</p>