manual/include/track-modes.html

<p>
  Audio tracks in Ardour have a <dfn>mode</dfn> which affects how they behave
  when recording:
</p>
<table class="dl">
  <tr><th>Layered</th>
  <td>Tracks in <dfn>layered mode</dfn> will record non-destructively&nbsp;&mdash;
  new data is written to new files, and when overdubbing, new regions will be
  layered on top of existing ones. This is the recommended mode for most
  workflows.
  </td></tr>
  <tr><th>Non-Layered</th>
  <td>Tracks using <dfn>non-layered mode</dfn> will record
  non-destructively&mdash;new data is written to new files, but when
  overdubbing, the existing regions are trimmed so that there are no overlaps.
  This does not affect the previously recorded audio data, and trimmed regions
  can be expanded again at will. Non-layered mode can be very useful for spoken
  word material, especially in combination with
  <a href="@@pushpull-trimming">push/pull trimming</a>.
  </td></tr>
  <tr><th>Sound on Sound</th>
  <td>Tracks using <dfn>sound-on-sound mode</dfn> will record
  non-destructively&nbsp;&mdash; new data is written to new files, but when
  overdubbing, new regions will be layered on top of existing ones in non-opaque
  mode which means both existing and new material will be played back after
  the recording is over. This is convenient for a variety of use cases, such as
  adding MIDI Control Change events on top of recorded live performance.
  </td></tr>
</table>

<p>
  Results of recording in layered and non-layered modes are visually the same.
  However, with the sound-on-sound mode lower layers are visible under upper
  layers, because in that case new regions with overdubs are created with
  disabled <em>Opaque</em> setting.
</p> 

<figure class="right">
  <img src="/images/region-layering-modes-overlaid.png" alt="Layered, non-layered, and sound-on-sound modes" width="75%" >
  <figcaption>
    Layered, non-layered, and sound-on-sound modes in overlaid view
  </figcaption>
</figure>

<p>
  To illustrate the difference, here is the screenshot of the same tracks, but
  this time&nbsp;&mdash; in <em>Stacked</em> track mode (rather than
  <em>Overlaid</em> as on the screenshot above).
</p>

<figure class="right">
  <img src="/images/region-layering-modes-stacked.png" alt="Layered, non-layered, and sound-on-sound modes in stacked view" width="75%" >
  <figcaption>
    Layered, non-layered, and sound-on-sound modes in stacked view
  </figcaption>
</figure>

<p>
  The overdub is an opaque region on top of the original content for the
  <em>Layered</em> mode. For the <em>Non-Layered</em> mode, it completely
  replaces the matching part of the original content. And for the
  <em>Sound on Sound</em> mode, it's a transparent region on top of the original
  content.
</p>

<p>
  The switch between layered, non-layered, and sound-on-sound modes is a global
  setting available in the main toolbar right below the buttons enabling
  Punch In and Punch Out.
</p>

<figure class="left">
  <img src="/images/layering-switch.png" alt="Layering switch" width="50%">
  <figcaption>
    Layering switch
  </figcaption>
</figure>