Basics

OSC lets synthesizers and other devices communicate with Ardour. OSC devices can send commands relating to playback (such as play or stop), performance (such as volume, play, stop), and almost any other function (such as Edit, or Undo).

Note: OSC control has changed dramatically since Ardour 4.7. The Path structure has been completely redone, Banking has been introduced, The controller is now able to tell Ardour what kind of feedback it can work with (including bank size) and the gain controls have new math calculations. If you are using an Ardour version of 4.7 or less, please read Osc control in Ardour 4.7 and prior.

Ardour is probably one of the most OSC-controllable audio applications around, but as with all OSC-controllable apps, you can't do much without knowing what messages can be sent. This document describes the various categories of messages that Ardour understands. It is subject to change, particularly the "Actions" part below, since this relates to the GTK GUI for Ardour rather than the backend.

Connecting to Ardour via OSC

OSC support is not enabled by default, but can be turned on via Edit > Preferences > Control Surfaces. Once enabled, Ardour will listen on port 3819 by default. This port number can be changed by editing $ARDOUR_CONFIG and adding this line within the <Config> section:

<Option name="osc-port" value="Your choice here"/>

Ardour sends any feedback to the port and address that sent any feedback request or to a port set manually in the setup dialog. The port does not have to match Ardour's port. In fact it is better not to. This means that Ardour can deal with more than one controller at a time. The two controllers can bank independently and even use different math for faders. This could be used to allow talent to adjust their own monitor mix using a tablet or phone that can run an OSC controller. For a full explanation of how Ardour's feedback works please read OSC feedback In Ardour.

Control Surface Set Up

Control surface set up allows the controller to tell Ardour about its capabilities. The surface can tell Ardour how many control strips it has for banking, if it is capable of setting its faders or buttons to values set by Ardour's GUI or automation, What kind of math the faders use and more.

Any time the /set_surface command is sent, the current bank is recalculated and if feedback is turned on, the values of each strip's controls are sent (or refreshed) as well. This will also refresh the Master feedback setup.

As of Ardour 5.1, There is now a GUI setup in response to those using tablets with applications such as touchOSC or AndrOSC who need to be able to set a port for Ardour to send to. It can also change the default setting for set_surface. For more information about Ardour's OSC configuration GUI please read Ardour's Setup Dialog.

If /set_surface is not sent, the default values are used:

  • Bank Size: 0 — No banking (or infinite bank size).
  • Strip Types: 159 — All strip types except hidden and special.
  • Feedback: 0 — All off.
  • Fader Mode: 0 — gain in dB (not relevant with feedback off)
  • Send Page Size: 0 — No Send Paging.
  • Plugin Page Size: 0 — No Plugin (parameter) Paging.
  • reply port: 8000 — control surface will receive feedback on port 8000
  • Link set: 0 — no linking for this control surface
  • Link ID: 0 — no link ID

These values give the same behaviour as prior versions of Ardour. (or the closest possible)

/set_surface bank_size strip_types feedback fadermode send_page_size plugin_page_size port linkset linkid

See below for an explanation of each parameter.

The /set_surface message may have all values except the last in-line. For example: /set_surface/8/31/8403/0/8 i 16 would be valid. Do be careful of switches which send a 0 on release, it may be necessary to set the value as the release value rather than the press value.

The /set_surface message may have less than the full set of parameters. those left out will remain as they were before the /set_surface message was sent. All parameters included must be valid. For example, setting send page size would require also setting bank_size, strip_types, feedback and gain mode. using only two parameters will set bank_size and strip_types. Sending /set_surface with no parameters will result in Ardour returning a /set_surface message with the current settings. Surfaces using /set_surface iiii b st fb gm as was the case in versions of Ardour older than 5.10 will continue to work.

bank_size

Bank Size is the number of channel strips the controller supports without banking. Setting this to 0 turns banking off by setting the bank size to infinite.

Bank size can also be set with /set_surface/bank_size size.

strip_types

strip_types is an integer made up of bits. The easy way to deal with this is to think of strip_types items being worth a number and then adding all those numbers together for a value to send. Strip Types will determine what kind of strips will be included in bank. This would include: Audio, MIDI, busses, VCAs, Master, Monitor and hidden or selected strips.

Aside from setting the track types for the main mix assignments, using /set_surface/strip_types with more than one surface button will allow switching between modes for example: inputs only, busses only, selected only, hidden only, by having the buttons send values of: 3, 12, 256, 512. A full mix button might have a value 31.

While Master and Monitor are listed as possibilities, most surfaces will not use them. Using /master and /monitor makes more sense. However, in the case where there are no master or monitor fader strips on the surface, it may be necessary to include them in the banked strips.

Please see: Calculating Feedback and Strip-types Values.

Strip types can also be set with /set_surface/strip_types types.

feedback

Feedback is an integer made up of bits. The easy way to deal with this is to think of feedback items being worth a number and then adding all those numbers together for a value to send.

Please see: Calculating Feedback and Strip-types Values.

Feedback can also be set with /set_surface/feedback feedback.

gainmode

Gainmode is an int:

  • 0: dB value as a float from -193 to +6. Sent as /strip/gain SSID value. (-193 or below are the same as −∞)
  • 1: A positional fader based on the same math as Ardour's GUI. A Float from 0 to 1. Sent as /strip/fader SSID value. At the same time the gain value in dB is sent to the channel name as text. The name will be restored after a short timeout.
  • 2: A positional fader based on the same math as Ardour's GUI. A Float from 0 to 1. Sent as /strip/fader SSID value. At the same time the gain value in dB is sent as /strip/gain SSID value.
  • 3: A positional fader based on the same math as Ardour's GUI. A Float from 0 to 1. Sent as /strip/fader SSID value.

Gainmode applies only to feedback values. The controller can choose which gain math to use by choosing to use the /*/gain or /*/fader path to send to Ardour. This makes sure a controller that doesn't set up Ardour's OSC can still use either math. The gainmode for feedback also determines the path Ardour uses for feedback so that the feedback messages match the control messages.

Gain mode can also be set with /set_surface/gainmode gainmode.

send_page_size

Send_page_size is an int for the number of send channels that can be controlled at one time. Each channel has a name, level and enable control. (added in Ardour 5.10)

Send page size can also be set with /set_surface/send_page_size send_page_size.

plugin_page_size

plugin_page_size is an int for the number of plugin controls that can be controlled at one time. Each control has a name and level. As each plugin is different (as is each parameter), the surface should expect to control the plugin parameters with a variable control (pot or slider) with a float value from 0 to 1 (even on/off switches). (added in Ardour 5.10)

Plugin page size can also be set with /set_surface/plugin_page_size plugin_page_size.

port

The port the controller would like to receive it's feedback on. Starting with Ardour 6.0, the surface can directly set the manual port or set it's host to auto port mode.

The value for port can be 0 for auto port mode or any port value above 1024. It is suggested not to use Ardour's port number of 3819 as controllers on the same machine that try to use the same port will fail.

If the surface does not tell Ardour which port to use, the default is 8000 or the setting set up in the OSC setup GUI. There can only be one port setting per host. If that setting is auto, than more than one controller can be run on that host, but if a manual port is set there can only be one. In the case of auto mode, the control surface must set it's receive port to be the same as it's send port. If that is not possible, then manual port mode must be used. This allows a smart controller to use a number of ports on the same ip while a smartphone set up as a personal monitor control can use the default manual port.

The host's port can also be set with /set_surface/port port.

Changing the port will remove feedback from a device on the same host using a different port.

Link set and Link ID

Please see Linking Surfaces For more information.

Querying Ardour for information

The control Surface may wish to control the type a frequency of updates it receives. It can do this with querying commands. See: Querying Ardour with OSC.

Using more than one surface

Ardour can use more than one surface at a time that both control the same controls in Ardour. It is also possible to use two surfaces in concert with each other. See: Linking Surfaces for more information.

List of OSC messages

Parameter types show how the value will be used. However, they may be sent as a different type if needed, see: Parameter Types in OSC.

This list shows all messages that can be sent to Ardour to control it. Most of these messages are also sent back as feedback when the corresponding value changes. There exist additional feedback-only messages, see: Feedback for more information.

Master or Global messages

Transport Control

/transport_stop Stops a rolling transport
/transport_play Puts transport in play mode
/toggle_roll Toggles between play and stop
/stop_forget Stop transport and delete/forget last take
/set_transport_speed speed where speed is a float ranging from -8.0f to 8.0f
/ffwd Adds 1.5 times to transport speed to maximum +8 times normal speed
/rewind Adds -1.5 times to transport speed to maximum -8 times normal speed
/goto_start Move playhead to start of session
/goto_end Move playhead to end of session
/jump_bars bars Where bars is a float (+/-) of the number of bars to jump
/jump_seconds seconds Where seconds is a float (+/-) of the number of seconds to jump
/toggle_click Toggle metronome click on and off
/marker marker Where marker may be a float or int of the nth marker or a string with the marker name to locate to (new Ardour 6.0). If the playhead is at a marker and the marker is unique, the marker at the playhead will be renamed to the string sent
/add_marker (adds marker to the current transport position)
/remove_marker Removes marker at the current transport position (if there is one)
/next_marker Move playhead to next marker
/prev_marker Move playhead to previous marker
/locate spos roll where spos is the target position in samples and roll is a bool/integer defining whether you want transport to be kept rolling or not
/loop_toggle Toggle loop mode on and off
/loop_location start end start is the beginning of a loop and end is the end of a loop both are integer frame positions.
/midi_panic Ardour will send an all notes off to all midi tracks
/cancel_all_solos Cancel All Solos/PFLs/AFLs

New for Ardour 5.9.

/scrub delta Where delta is a float indicating forward or reverse movement. See OSC Scrub Modes
/jog delta Where delta is a float indicating forward or reverse movement
/jog/mode mode Where mode is an int from 0 to 7 indicating what the /jog command controls. See OSC Jog Modes

Recording control

/toggle_punch_in
/toggle_punch_out
/rec_enable_toggle Toggles master record enable

Transport Information

/transport_frame Ardour sends /transport_frame current_frame
/transport_speed Ardour sends /transport_speed speed
/record_enabled Ardour sends /record_enabled recordenable_status

Editing-related

/undo
/redo
/save_state (this is the regular Session > Save operation)
/session_name new_name Set session name to new_name (if new_name is legal and unique)

Master and Monitor strip control

/master/gain dB dB is a float indicating the desired gain in dB
/master/fader position position is a float between 0 and 1 setting the desired position of the fader
/master/db_delta delta where delta is a float that will increase or decrease the gain of master by the amount of the delta. (Ardour 5.11+)
/master/trimdB dB dB is a float from -20 to +20 representing the desired trim gain in dB
/master/pan_stereo_position position position is a float from 0 to 1 representing the desired pan position
/master/mute key key is an optional float 1 representing a master bus select
/master/select state state is an int of o or 1 representing the desired mute state
/monitor/gain dB dB is a float indicating the desired gain in dB
/monitor/fader position position is a float between 0 and 1 setting the desired position of the fader
/monitor/db_delta delta where delta is a float that will increase or decrease the gain of monitor by the amount of the delta. (Ardour 5.11+)
/monitor/mute state state is an int of 0 or 1 where 1 is muted
/monitor/dim state state is an int of 0 or 1 where 1 is dimmed
/monitor/mono state state is an int of 0 or 1 where 1 is mono mode

Track specific operations

For each of the following, ssid is the Surface Strip ID for the track

As of Ardour 6.0, the user may use a subset all available strips. See: Making a user selected strip list.

SSID has a different meaning than RID in Ardour version 4.7 and before. Effectively, banking is always being used and the SSID is generated on the fly. The SSID is the position of the strip within bank as an int 1 to bank size. There are no gaps as there have been in the past. Depending on the value of strip_types sent to Ardour, Master and Monitor, may be included in the list of SSIDs or not as set in /set_surface.

Some Surfaces (many Android applets) are not able to deal with more than one parameter in a command. However, the two parameter commands below can also be sent as /strip/command/ssid param. In this case the param should be a float even if an int is required below.

/bank_up Change bank to the next higher bank.
/bank_up delta Where delta is a float of 1 to bank up and -1 is bank down for use with an encoder (Ardour 5.11+)
/bank_down Change bank to the next lower bank.
/use_group state Where state is a float of 1 to use group or 0 to not use group. more info on use_group
/strip/spill ssid Use strips this strip is grouped with or those that feed this bus (if this strip is a bus) or that this vca (if this is a VCA) controls. See Spill Strips for more details
/strip/hide ssid y/n Where y/n = 1 hide this strip, 0 for show this track. Hiding strips.
/strip/name ssid strip_name where strip_name is a string representing the desired name for the strip
/strip/group ssid group_name where group_name is a string representing the name of the group desired. See groups for more details
/strip/mute ssid mute_st where mute_st is a bool/int representing the desired mute state of the track
/strip/solo ssid solo_st where solo_st is a bool/int representing the desired solo state of the track
/strip/solo_iso ssid state where state is a bool/int representing the desired solo isolate state of the track
/strip/solo_safe ssid state where state is a bool/int representing the desired solo safe/lock state of the track
/strip/monitor_input ssid monitor_st where monitor_st is a bool/int where 1 is forced input monitoring.
/strip/monitor_disk ssid monitor_st where monitor_st is a bool/int where 1 is forced disk monitoring. When input and disk are both off, Auto monitoring is enabled.
/strip/recenable ssid rec_st where rec_st is a bool/int representing the desired rec state of the track
/strip/record_safe ssid rec_st where rec_st is a bool/int representing the desired record safe state of the track
/strip/polarity ssid invert where invert is a bool/int representing the desired polarity of the track
/strip/gain ssid gain where gain is a float ranging from -193 to 6 representing the desired gain of the track in dB.
/strip/fader ssid position where position is a float ranging from 0 to 1 representing the fader control position.
/strip/db_delta ssid delta where delta is a float that will increase or decrease the gain of a track by the amount of the delta. (Ardour 5.11+)
/strip/*/automation ssid mode where mode is an int ranging from 0 to 3 representing the desired automation mode for the control. See OSC Automation.
/strip/*/touch ssid state where state is an int of 1 for touched and 0 for released. See OSC Automation.
/strip/trimdB ssid trim_db where trim_db is a float ranging from -20 to 20 representing the desired trim of the track in dB.
/strip/pan_stereo_position ssid position where position is a float ranging from 0 to 1 representing the desired pan position of the track
/strip/pan_stereo_width ssid width where width is a float ranging from 0 to 1 representing the desired pan width of the track
/strip/send/gain ssid sendid send_gain where sendid = nth_send, send_gain is a float ranging from -193 to +6 representing the desired gain in dB for the send
/strip/send/fader ssid sendid send_gain where sendid = nth_send, send_gain is a float ranging from 0 to 1 representing the desired position for the send as a fader
/strip/send/enable ssid sendid state where sendid = nth_send, state is 1 for enabled and 0 for disabled
/strip/list see: Querying Ardour with OSC.
/strip/sends ssid see: Querying Ardour with OSC.
/strip/receives ssid see: Querying Ardour with OSC.
/strip/plugin/list ssid see: Querying Ardour with OSC.
/strip/plugin/descriptor ssid see: Querying Ardour with OSC.
/strip/plugin/reset ssid piid where piid = nth Plugin, will reset all values to the plugin's original values
/strip/plugin/activate ssid piid where piid = nth Plugin, will set the plugin's state to active
/strip/plugin/deactivate ssid piid where piid = nth Plugin, will set the plugin's state to inactive
/strip/plugin/parameter ssid piid param value where piid = nth Plugin, param = nth param, value is a float ranging from 0 to 1 representing the desired parameter value
/strip/name ssid name where name is a string for the desired name of the track

Selected Strip Operations

New for Ardour 5, A whole set of operations that work on the selected or expanded strip.

Selected strip operations are complex enough for their own page. Please read: Selection Considerations in OSC. This is most important if more than one OSC surface is being used with Ardour.

There are two kinds of selection in OSC. GUI selection and local expansion. By default expansion follows selection.

  • GUI selection: Use /strip/select to set. Selecting a strip in the GUI will set OSC surface select and the surface will set GUI selection as well.
  • Local expansion: Use /strip/expand to expand a strip without changing overall selection. When /strip/expand is set to 0 or false, the select channel will go back to using the strip selected by the GUI. While expand is turned on, selecting a strip on the GUI does not select the OSC strip. Sending a /strip/select message will override the expand as if it had been set to false. Good for more than one OSC controller at a time.

/strip/select ssid y/n Where y/n = 1 for select. Sets both GUI select and strip to expanded mode. (0 is ignored)
/strip/expand ssid y/n Where y/n = 1 for expanded mode. Sets only local strip to Expanded. Setting to 0 resets the expansion to follow selection.
/select/expand y/n Where y/n = 1 for expanded mode, 0 for Select mode.
/select/hide y/n Where y/n = 1 hide this strip, 0 for show this track. Hiding strips.
/select/name strip_name where strip_name is a string representing the desired name for the strip
/select/comment comment where comment is a string representing the desired comment for the strip
/select/group group_name where group_name is a string representing the name of the group desired. See groups for more details
/select/group/enable state where state is an int representing the desired enable state of the group the selected strip is a part of
/select/group/gain state where state is an int which sets the gain sharing of the group the strip belongs to. See Track and Bus Groups for more details
/select/group/relative state where state is an int which sets relative state of thew group the strip belongs to. See Track and Bus Groups for more details
/select/group/mute state where state is an int which sets the mute sharing of the group the strip belongs to. See Track and Bus Groups for more details
/select/group/solo state where state is an int which sets the solo sharing of the group the strip belongs to. See Track and Bus Groups for more details
/select/group/recenable state where state is an int which sets the recenable sharing of the group the strip belongs to. See Track and Bus Groups for more details
/select/group/select state where state is an int which sets the select sharing of the group the strip belongs to. See Track and Bus Groups for more details
/select/group/active state where state is an int which sets the route active sharing of the group the strip belongs to. See Track and Bus Groups for more details
/select/group/color state where state is an int which sets the color sharing of the group the strip belongs to. See Track and Bus Groups for more details
/select/group/monitoring state where state is an int which sets the monitoring sharing of the group the strip belongs to. See Track and Bus Groups for more details
/select/recenable y/n Where y/n is 1 for enabled and 0 for disabled
/select/record_safe y/n Where y/n is 1 for safe and 0 for unlocked
/select/mute y/n Where y/n is 1 for enabled and 0 for disabled
/select/solo y/n Where y/n is 1 for enabled and 0 for disabled
/select/solo_iso state where state is a bool/int representing the desired solo isolate state of the track
/select/solo_safe state where state is a bool/int representing the desired solo safe/lock state of the track
/select/monitor_input y/n Where y/n is 1 for monitor from input and 0 for auto
/select/monitor_disk y/n Where y/n is 1 for monitor from disk and 0 for auto
/select/polarity invert where invert is a bool/int representing the desired polarity of the track
/select/gain gain Where gain is a float ranging from -193 to 6 representing the desired gain of the track in dB.
/select/fader position Where position is an float ranging from 0 to 1 representing the fader control position.
/select/db_delta delta where delta is a float that will increase or decrease the gain of the selected track by the amount of the delta. (Ardour 5.11+)
/select/vca name state where name is a string with the name of the VCA, and state is an int that determines if the named VCA will control this strip. (Ardour 6.0)
/select/vca/toggle name where name is a string with the name of the VCA. This toggles the use of the named vca with this strip. Any trailing "[_]" will be ignored. (Ardour 6.0)
/select/spill show only strips this strip is grouped with or those that feed this bus or that this vca controls. See Spill Strips for more details
/select/*/automation mode where mode is an int ranging from 0 to 3 representing the desired automation mode for the control. See OSC Automation.
/select/*/touch state where state is an int of 1 for touched and 0 for released. See OSC Automation.
/select/trimdB trim_db where trim_db is a float ranging from -20 to 20 representing the desired trim of the track in dB.
/select/pan_stereo_position position where position is a float ranging from 0 to 1 representing the desired pan position of the track
/select/pan_stereo_width width where width is a float ranging from 0 to 1 representing the desired pan width of the track
/select/pan_elevation_position position where position is a float ranging from 0 to 1 representing the desired pan elevation of the track
/select/pan_frontback_position position where position is a float ranging from 0 to 1 representing the desired front to back position of the track
/select/pan_lfe_control value where value is a float ranging from 0 to 1 representing the desired LFE control value for the track
/select/send_gain sendid send_gain where sendid = nth_send, send_gain is a float ranging from -193 to +6 representing the desired gain in dB for the send
/select/send_fader sendid send_gain where sendid = nth_send, send_gain is a float ranging from 0 to 1 representing the desired position for the send as a fader
/select/send_enable sendid state where sendid = nth_send, state is 1 for enabled and 0 for disabled
/select/send_page delta where delta is an int or float selecting another send as a delta from the current send.

/select/send_page and /select/plugin_page may be used with a page up and page down switch by using a switch with a value of 1 for page up and a switch with a value of -1 for page down. An encoder can be used as well. (these commands were added in Ardour version 5.10)

Selected Plugin Operations

These operations control the selected plugin on the selected strip. Plugins and parameters are specified by their position in the list of plugins and controllable parameters. Parameters are paged to allow accessing all parameters on a surface with limited inputs, the plugin (parameter) page size is configured with /set_surface.

When the selected strip is changed, the plugin in the same position in the newly selected strip is made the selected plugin (even if it is a different type of plugin). If the new strip has fewer plugins, the last plugin is selected. If the new strip has no plugins, no plugin is selected.

/select/plugin delta where delta is an int or float selecting another plugin as a delta from the currently selected plugin index.
/select/plug_page up_or_down where up_or_down is 1 for page up or -1 for page down (0 is ignored).
/select/plugin/activate y/n where y/n is 1 for activating and 0 for deactivating the selected plugin. (new Ardour 6.0)
/select/plugin/parameter piid paid value
/select/plugin/parameter paid value
/select/plugin/parameter/piid/paid value
/select/plugin/parameter/paid value 		where piid = nth plugin, paid = nth parameter and value is a float from 0 to 1. If piid is omitted, the currently selected plugin is used. Otherwise, the specified plugin is made the selected plugin and its parameter modified.
Feedback messages omit the piid argument. The paid is normally passed as an argument (second form) but can be put in the path (last form) using the /set_surface/feedback state command. See Calculating Feedback and Strip-types Values.

The paid argument is specified as a 1-based index into the list of controllable parameters only (as specified by the controllable flag in the /strip/plugin/descriptor query message, skipping non-controllable-only parameters).

Using groups with strip and select (new for Ardour 6.0)

No grouping will occur unless use_group is set either by using /set_surface/strip_types with the use groups bit set or by using /use_group i 1.

The result for /strip/group or /select/group is determined by the parameter passed in the command and the current group and available list of groups. The group name the control surface sends may be:

  • "none", "" or " " will remove this strip from this group. If this was the only strip in this group, the group is deleted. Some OSC controllers have trouble sending an empty string and a list of groups contains "none" as well so a dropdown can just send a text item and work.
  • The name of a group this strip does not belong to will remove this strip from it's current group and add it to the named group. If this strip was the only strip in the group it was removed from, that group will be deleted.
  • An unused name when this strip is not part of a group will create a new group with the group name sent and add this strip to that group
  • An unused name when this strip is already a part of a group will rename this group to the name sent.

To create a new group from a strip that is already joined to a group, the strip must first remove itself from the current group.

Spill Strips

/select/spill or /strip/spill will:

  • set the current set of strips in use to include only the strips that are a part of the group the strip is a part of so long as that strip is a track.
  • set the current set of strips to the set of strips that feed this strip if it is a bus. In the case where this strip is being fed by sends rather than strip outputs, the strips that feed this bus will have their names set to the name of the strip with -send appended to it and the fader, pan and mute will control the send rather than the strip. The other strip controls will be disabled in this mode. This only happens when the strip that calls spill is a bus. In the case where a strip that is part of a group is chosen as above where the group all sends to a common bus this will not happen. This can be useful for a group that uses "Add New Aux Bus" to switch from sends to faders.
  • set the current set of strips to the set of strips that are controlled by the VCA if this strip is a VCA.

spill/group, spill/bus or spill/vca can also be used to force the type of spilling that is done. This may be useful if the strip is a bus that is a part of a group and the group variation is required.

In all cases, if there is a bus or VCA attached to the group of strips it will be included as well.

What is less obvious, is how to return to the normal set of strips. There are a number of ways of doing so depending on the operator's wishes. The most obvious way is to use /set_surface/strip_types to set the strip list as desired. It is expected that a control surface may have more than one strip types button in any case to see only inputs or only busses etc and of course one to give a full mix. Another option is to reselect the custom set of strips with /strip/custom/mode mode.

Controlling plugins

Menu actions

Every single menu item in Ardour's GUI is accessible via OSC. There is a single common syntax to trigger the action as if it was selected with the mouse (or keyboard):

/access_action action_name

As of Ardour 5.9, access_action can be inlined for control surfaces that are unable to send string parameters. The action_name is composed of a group and an action in the form of Group/action which fits very well as an OSC path extension:

/access_action/Group/action key_pressed

The key_pressed is optional, but if present is a float 1 or 0 where the command is ignored if key_pressed is 0.

Some of the Menu Actions duplicate other OSC commands. In all cases it is better to use the OSC commands rather than the Menu Actions if possible as the OSC commands are more direct.

The list of actions shows all available values of action-name for Ardour.