manual/include/tempo-ruler.html

<p>
  The Tempo ruler allows changing tempo within one session, either abruptly or
  gradually over time. This is done by placing tempo markers on the ruler and
  setting up how exactly the transition happens. Alternatively, in the
  <a href="/ardours-interface/the-toolbox#grid">Grid mode</a>, markers can be
  added and edited directly on the timeline.
</p>

<p>
  On the screenshot below, there are 4 bars of music at 120bpm starting at bar 27,
  then the tempo changes abruptly to 140bpm and goes on for another 4 bars at that
  tempo, then abruptly changes back to 120bpm and within the next 4 bars gradually
  goes back to 140bpm, then continues at 140bpm until the end of the session.
</p>

<figure>
  <img style="width:75%;" width="50%" src="/images/multiple-tempo-markers.png"
  alt="Changes in tempo over time">
  <figcaption>Changes in tempo over time</figcaption>
</figure>

<h2>Anatomy of tempo markers</h2>

<p>
	Each tempo marker exposes several editable properties:
</p>

<ul>
	<li>
		BPM at the start, sets a new tempo value.
	</li>
	<li>
		BPM at the end <em>(only available for gradual transitions)</em>, defines
		the tempo value at the end of a tempo ramp.
	</li>
	<li>
		Tempo (transition) type, defines whether the tempo is the same (constant)
		until the next tempo marker or whether it gradually changes (ramps up
		or down) towards the next tempo.
	</li>
	<li>
		Location of the tempo marker, defined in musical time.
	</li>
	<li>
		Lock style, defines whether tempo is locked to musical time (bars and
		beats) or real time (minutes and seconds).
	</li>
</ul>

<h2>Working with tempo markers on the ruler</h2>

<h3>Adding Tempo Markers</h3>

<p>
	To add a tempo marker, hover a bar or a beat line, press <kbd>Ctrl</kbd>
	and single-click. Newly created tempo marker will have the same tempo value
	as the previous one.
</p>

<h2>Shifting tempo markers</h2>

<p>
	To change the position of a tempo change, do one of the two things:
</p>

<ul>
	<li>
		Click and drag a marker left or right. Ardour will increment the change
		by one beat.
	</li>
	<li>
		Double-click the marker or right-click it and choose
		<kbd class="menu">Edit</kbd> to open the marker properties dialog, then
		change the bar and the beat where tempo change should occur.
	</li>
</ul>

<figure>
  <img style="width:50%;" width="50%" src="/images/tempo-marker-change-location.png"
  alt="Changing location of a tempo marker">
  <figcaption>Changing location of a tempo marker</figcaption>
</figure>

<h3>Editing tempo value</h3>

<p>
	The tempo start value can be changed directly on the timeline or using the
	tempo marker properties dialog.
</p>

<p>
	To change the tempo value directly on the timeline, hover the marker, press
	<kbd>Ctrl</kbd>, and drag the marker left or right. The bpm start value will
	change, and the grid will be adjusted accordingly.
</p>

<p>
	Alternatively, double-click the marker or right-click it and choose
	<kbd class="menu">Edit</kbd> to open the marker properties dialog, then
	change the "Start beats per minute" value.
</p>

<p>
	Additionally, you can set the new tempo by tapping it in one of the two ways:
</p>

<ul>
	<li>
		By repeatedly clicking the <kbd class="button">Tap tempo</kbd> button
		in the dialog.
	</li>
	<li>
		By selecting a connected MIDI keyboard and repeatedly pressing either
		a piano key or a silicon pad.
	</li>
</ul>

<p>
	In some cases, an existing tempo marker needs to get the same value as the
	tempo marker before it, typically to start a ramp. To do that, right-click
	the tempo marker that needs to change and select the
	<kbd class="menu">Continue</kbd> menu item.
</p>

<h3>Constant vs ramped tempo</h3>

<p>
	The tempo between two tempo markers with different bpm start values can stay
	the same (constant) or change gradually (ramped).
</p>

<p>
	When the tempo type is constant, the line between two markers stays
	horizontal:
</p>

<figure>
  <img style="width:75%;" width="75%" src="/images/tempo-type-constant.png"
  alt="Constant tempo">
  <figcaption>Constant tempo</figcaption>
</figure>

<p>
	When the tempo is ramped, the line between two markers is diagonal:
</p>

<figure>
  <img style="width:75%;" width="75%" src="/images/tempo-type-ramped.png"
  alt="Ramped tempo">
  <figcaption>Ramped tempo</figcaption>
</figure>

<p>
	The toggle between constant and ramped types is available in the tempo marker
	properties menu and applies forward in the timeline. Alternatively, you can
	right-click a tempo marker and select the <kbd class="menu">Ramp to Next</kbd>
	menu item. Tempo will gradually accelerate or decelerate until the target
	tempo is reached, resulting in a musical <em>accel.</em> or <em>ritard.</em>
</p>

<p>
	To switch from the ramped type to the constant type, either open the tempo
	marker properties dialog and switch it, or right-click a tempo marker and
	select the <kbd class="menu">Set Constant</kbd> menu item. The tempo will
	change abruptly at the next tempo marker.
</p>

<h3>Removing Markers</h3>

<p>
	To remove a tempo marker, either single-click it and press <kbd>Del</kbd>
	or right-click it and select the <kbd class="menu">Remove</kbd> menu item.
</p>

<h3>Locking to music vs audio time</h3>

<p>
	Audio-locked tempo markers stay in their frame position as their neighbor's
	positions are altered. Their pulse (musical) position will change as their
	neighbors move. Music-locked tempo markers move their frame position as their
	neighbors are moved, but keep their pulse position (they will move as the
	music is moved).
</p>

<h2>Working with tempo markers in the Grid mode</h2>

<p>
	For documentation on editing the tempo map in the Grid mode, please see
	the <a href="/ardours-interface/the-toolbox#grid">relevant part</a> of the
	Toolbox chapter.
</p>

<h2>Further Information</h2>

<p>
  For more details on the workflow, please refer to the
  <a href="@@tempo-and-meter">Tempo and Time Signature</a> chapter.
</p>