manual/include/midi-on-linux.html

<p>
  The right approach for using MIDI on Linux depends on which version of JACK
  is in use. The world divides into:
</p>

<table class="dl">
  <tr><th>Systems using JACK 1, versions 0.124 or later</th>
  <td>On these systems, simply start JACK with the <code>-X alsa_midi</code>
  server argument. To support legacy control applications, the <code>-X
  seq</code> argument to the ALSA backend of JACK can also be used to get the
  exact same results.</td></tr>
  <tr><th>All others</th>
  <td>Use a2jmidid to act as a bridge between ALSA MIDI and JACK. Do not use
  the <code>-X seq</code> or <code>-X raw</code> arguments&mdash;the timing and
  performance of these options is unacceptable.</td></tr>
</table>

<h2>Using a2jmidid</h2>

<p>
  <dfn>a2jmidid</dfn> is an application that bridges between the system
  <abbr title="Musical Instrument Digital Interface">MIDI</abbr> ports and
  <abbr title="JACK Audio Connection Kit">JACK</abbr>.
</p>

<p>
  First it must be ensured that there is no ALSA sequencer support enabled in
  JACK. To check that, open QJackCtl's <kbd class="menu">Setup</kbd> window.
  Set <kbd class="menu">Settings &gt; MIDI Driver</kbd> to <kbd
  class="input">none</kbd>. Then uncheck the <kbd class="optoff">Misc &gt;
  Enable ALSA Sequencer support</kbd> option. Now restart the jack server
  before going on.
</p>

<h3>Check for a2jmidid availability</h3>

<p>
  Next, check whether a2jmidid is already installed. After starting the JACK
  server, go to the command line and type:
</p>

<kbd class="cmd lin">a2jmidid -e</kbd>

<p>
  If a2jmidid does not exist, install it with the software manager of the
  Linux distribution in use and try again.
</p>

<h2>Check available MIDI ports</h2>

<p>
  If JACK is correctly configured for MIDI, then the MIDI ports should appear
  in qjackctl under <kbd class="menu">Connections &gt; MIDI</kbd>.
</p>

<h3>Making it automatic</h3>

<p>
  Once it has been verified that the ports appear in JACK as expected, this can
  be made to happen whenever JACK is started:
</p>

<ul>
  <li>If a newer version of JACK 1 is in use, just make sure the <code>-X
  alsa_midi</code> or <code>-X seq</code> options are enabled for whatever
  technique is being used to start JACK.</li>
  <li>For other versions of JACK, add <code>a2jmidid -e &amp;</code> as an
  "after start-up" script in the <kbd class="menu">Setup &gt; Options</kbd> tab
  of QJackCtl, so that it is started automatically whenever JACK is
  started.</li>
</ul>