manual/include/automation-states.html

<p>
  In order to understand how automation in Ardour works, it is necessary to
  understand the four states of automation. They are: <kbd
  class=menu>Manual</kbd>, <kbd class=menu>Play</kbd>, <kbd
  class=menu>Write</kbd>, and <kbd class=menu>Touch</kbd>.
</p>

<figure class=right>
<img src="/images/automation-modes1.png">
<figcaption class=center>The automation state menu.</figcaption>
</figure>

<p>
  <kbd class=menu>Manual</kbd> state is basically analogous to a processor's
  bypass switch. Whenever an automation lane is in this state, it is inactive
  and any level that is manually set for controlling the lane's parameter will
  persist during playback like normal.
</p>

<p class=note>
  In Ardour, every track and processor parameter is initially set to <kbd
  class=menu>Manual</kbd> state.
</p>

<p>
  <kbd class=menu>Play</kbd> state tells Ardour to use the automation curve in
  the automation lane to control the level of the parameter controlled by the
  lane <em>during playback</em>. The control that normally sets the parameter
  will be <em>unresponsive to manual input</em> and will move automatically in
  accord with the lane's automation curve during playback.
</p>

<p>
  <kbd class=menu>Write</kbd> state allows continuous, dynamic setting of a
  control during playback; all such settings are written to the lane the
  control is in. This defines the lane's automation curve in the interval being
  played, and overwrites any existing automation curve in the lane being
  manipulated.
</p>

<p>
  <kbd class=menu>Touch</kbd> state is similar to <kbd class=menu>Write</kbd>
  mode, except it only overwrites sections of a lane's automation curve when
  the control is changed in some way. This allows for changing only the parts
  of an automation curve that are desired to be changed, while leaving the rest
  unchanged.
</p>