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, JACK must be started 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>Using a2jmidid acts as a bridge between ALSA MIDI and JACK. The <code>-X seq</code>
  or <code>-X raw</code> arguments should <em>not</em> be used&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, one must open QJackCtl's <kbd class="menu">Setup</kbd> window
  and 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. The jack server must then be restarted
  before going on.
</p>

<h3>Checking for a2jmidid availability</h3>

<p>
  Next, it must be checked whether a2jmidid is already installed. This is done
  by starting the JACK server, then going to the command line and typing:
</p>

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

<p>
  If a2jmidid does not exist, it must be installed with the software manager of the
  Linux distribution in use until this command responds.
</p>

<h2>Checking 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, by just making 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, by adding <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>