manual/include/techniques-for-working-with-tempo-and-meter.html

<h2>Matching a recorded tempo with a tempo ramp</h2>

<figure class="left">
  <img class="mini" src="/images/tempo-ramp_1.png" alt="Initial state">
  <figcaption>Initial state.</figcaption>
</figure>

<p>
  As a general approach, the best way to control tempo ramps is to use them in
  pairs.
</p>

<p>
  One typical use of tempo ramps is to match the click to a drum performance
  recorded in 'free time', like in the (admittedly bad) 4/4 example on the left.
</p>

<h3 class="clear">Step 1: First time signature</h3>

<figure class="left">
  <img class="mini" src="/images/tempo-ramp_2.png" alt="Step 1/5">
  <figcaption>Placing the first time signature</figcaption>
</figure>

<p>
  The first thing needed is determining where the first beat is in the recording
  and <kbd class="mouse">left</kbd> dragging the first time signature to that
  position.
</p>

<h3 class="clear">Step 2: Locating the <em>n</em>th bar</h3>

<figure class="left">
  <img class="mini" src="/images/tempo-ramp_3.png" alt="Step 2/5">
  <figcaption>Locating a known beat</figcaption>
</figure>

<p>
  Now the first click will be in time with the first beat. By listening to the
  recorded drums, the position of bar <em>n</em> (here, 9th beat, 3rd bar) is
  visually located (the playhead may be moved to this location to "pin" it).
</p>

<h3 class="clear">Step 3: Aligning the ruler with the tempo</h3>

<figure class="left">
  <img class="mini" src="/images/tempo-ramp_4.png" alt="Step 3/5">
  <figcaption>Matching the tempi</figcaption>
</figure>

<p>
  Holding the constraint modifier (<kbd class="mod3n"></kbd> by default, may be
  changed in <kbd class="menu">Preferences &gt; Editor &gt; Modifiers</kbd>),
  the third bar marker in the BBT ruler is dragged at the position of the third
  bar in the recording (where the playhead is located). This drag can be done
  either in the Time Signature or in the Tempo rulers. The tempo (on the first
  and only tempo marker) reflects the new value based on this change.
</p>

<p>
  The click now matches the first 8 beats, but after that it can wander off,
  which will be reflected in the tempo lines thet won't quite match the drum
  hits.
</p>

<h3 class="clear">Step 4: Placing a new tempo marker</h3>

<figure class="left">
  <img class="mini" src="/images/tempo-ramp_5.png" alt="Step 4/5">
  <figcaption>Creating a tempo marker</figcaption>
</figure>

<p>
  A new tempo marker is placed on the last position where the click matches the
  recorded audio, by <kbd class="mod1n"></kbd>-clicking the Tempo ruler. This
  will "anchor" the value of the tempo at that position.
</p>

<h3 class="clear">Step 5: Placing another tempo marker at the <em>n</em>th beat</h3>

<figure class="left">
  <img class="mini" src="/images/tempo-ramp_6.png" alt="Step 5/5">
  <figcaption>Placing another marker</figcaption>
</figure>

<p>
  Another tempo marker is placed <em>n</em> beats after the previous marker
  (here, 4 beats, 1 bar).
</p>


<h3 class="clear">Step 6: Changing the tempo to a new value</h3>

<figure class="left">
  <img class="mini" src="/images/tempo-ramp_7.png" alt="Step 5/5">
  <figcaption>Adjusting the tempo</figcaption>
</figure>

<p>
  Now, <kbd class="mod3n"></kbd>-dragging any beat <strong>after</strong> the
  second new tempo marker will allow to align the drum audio and tempo after the
  second marker.
</p>

<h3 class="clear">Step 7: Ramping the tempo change</h3>

<figure class="left">
  <img class="mini" src="/images/tempo-ramp_8.png" alt="Step 5/5">
  <figcaption>Ramping the change</figcaption>
</figure>

<p>
  Although it may be unnecessary in some cases where the tempo changes abruptly,
  most of the time, the tempo change is progressive in time, like an
  instrumentist drifting in tempo. In those cases, the tempo change should be
  progressive too, and Ardour allows that by ramping the tempo change.
</p>

<p>
  <kbd class="mouse">Right</kbd>-clicking the first tempo marker, a menu appears,
  allowing to <kbd class="menu">Ramp to Next</kbd>. This will make the tempo
  between the two markers linearly change from the first marker's value to the
  second's.
</p>

<p>
  Again, some time later the click will probably drift again, so the same
  technique has to be repeated: adding two new tempos and dragging the BBT ruler
  <strong>after</strong> the newest tempo so that the beats align with the audio
  again.
</p>

<p>
  In a general sense, adding tempo markers in pairs allows to 'pin' the tempo at
  the marker's location while moving further to the right.
</p>

<h2>Other use cases</h2>

<p>
  Audio-locked time signatures can be useful when composing, as they allow a
  continuous piece of music to be worked on in isolated segments, preventing the
  listening fatigue of a fixed form. Reassembly is left as an exercise for the
  reader.
</p>

<p>
  Tempo ramps can also be used in a video context, e.g. for an accelerando, by
  snapping to TC frames and dragging the ruler so that a bar ends up on a
  significant video frame.
</p>