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 meter</h3>

<figure class="left">
  <img class="mini" src="/images/tempo-ramp_2.png" alt="Step 1/5">
  <figcaption>Placing the first meter</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 meter 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 Preferences->Editor->Modifiers), 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 Meter
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 meters 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 excercise 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>