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 with the mouse, simply enter draw mode (press
  "d" or click on the pencil tool) and then <kbd
  class="mouse">Left</kbd>-click in a MIDI track. This creates a region 
  that is one bar long. Alternatively, use the left button to
  drag-create a new region of the desired length.
</p>
<p>
  Once the region exists, to trim it to a different length, switch
  back to grabber/object/select mode (press "g" or click on the
  grabber tool). Then <a href="@@trimming-regions">trim</a> to your desired length.
</p>
<p>
  Once the region is ready, <a href="@@add-new-notes">add some notes</a>
  to it.
</p>