The transport controls

The Transport Bar groups all the actions regarding the control of playback and recording.

The transport controls
The transport controls

Transport action buttons

The upper row contains transport actions, that are all bound to keyboard shortcuts, which allows for speedier use and more focused work:

Midi PanicImmediately stops all midi output.
Enable/disable Audio ClickToggles (on/off) a click track (metronome) along the tempo. Right clicking brings up the Click submenu from the Preferences. Scrolling with the mouse wheel adjusts the gain of the click.
Go to Start of the SessionJumps back at the beginning of the session, as defined by the start marker.
Go to End of the SessionJumps forward to the end of the session, as defined by the end marker.
Play Loop RangeRepeats the defined loop as defined by the Loop range, until the "Stop playback" button is pressed. Clicking the "Play loop Range" button while already active switches to normal Play mode, which exits the loop without stopping and restarting playback.
Play Range/SelectionIf a range has been defined using the Range Mode button, plays the range, of if an audio or MIDI region is selected, plays this region. In both cases, the playback stops at the end of the range or selected region.
Play from playheadStarts the playback and optionally record (more below).
StopWhatever the playing mode (loop, range, …) stops all playback. Depending on other settings, some effects (like chorus or reverb) might still be audible for a while.
Toggle RecordGlobal switch button to activate/deactivate recording. While active, the button blinks red. The button doesn't start recording by itself: if one or more tracks are marked as record-enabled, pressing the "Play from Playhead" starts recording on those tracks.

If Ardour is synchronized with other devices then some or all of these control methods may be unavailable—depending on the synchronization protocol, Ardour may respond only to commands sent from its master device(s).

The Transport modifiers

The Shuttle Speed Control

Under these buttons is the Shuttle Speed Control that allows to temporarily scrub through the audio quickly. The slider decides the playback speed: the further from the center it is set, the faster the playback will scrub in both directions. The range of this acceleration can be set by right-clicking the control and setting the multiplier, either 1.5 (± 150%) or 2 (± 200%).

VariSpeed

The VS (for VariSpeed) button sets a constant playback/record speed. It can be set in semitones (1 semitone = × 2 1⁄12 ≈ 105,9%), cents of semitones, or percentages, and is armed/disarmed by clicking the button. The VS button will blink when VariSpeed is enabled. Whether or not this VariSpeed is persistent when stopping/restarting transport depends on the Reset default speed on stop parameter in the Preferences dialog.

Transport Sync

On the left of the slider is the positional sync button (which might show Internal, or MTC or several other values), than can be used to control whether or not the transport position and start is controlled by Ardour, or by an external positional synchronization source, such as MIDI Time Code (MTC), Linear Time Code (LTC) or JACK (see Timecode Generators and Slaves).

Transport Status

The current playback status (Stop, Play, or speed %) is shown on the right of the speed slider.

Using Key Bindings

Ardour has many available commands for playback control that can be bound to keys. Many of them have default bindings, some do not, so the list below shows both the default bindings and internal command names for some of them.

SpaceSwitch between playback and stop.
HomeMove playhead to session start marker
EndMove playhead to session end marker
Playhead to next region boundary
Playhead to previous region boundary
0Move playhead to start of the timeline

The Transport and Transport > Playhead menus contain a lot more transport actions and their key bindings.