Live API Overview
Basic information about the Live API and links to further readings.
This document refers to Ableton Live version 11 or newer.
Besides building new instruments and effects to be used in Live, Max For Live also allows to access Live itself, its tracks, clips, devices and hardware control surfaces. This chapter defines some basic terms used throughout the whole Live API and introduces the Max objects representing the Live API.
Live Object Model
The accessible parts of Live are represented by a hierarchy of objects called the Live Object Model (LOM).
The model describes the hierarchy of objects inside Live, as seen from the Max devices. There are various types of objects in the model, like or . For certain objects only a single instance exists, for other multiple instances are held in lists.
The Live Object Model reference shows how to navigate from a number of root objects down a path to the particular object of interest, and what to do with it. Not all of Live's parameters are accessible via Live's API, the reference should give you an idea of what can and can't be done via Max for Live.
Live objects are accessed using paths according to the Live Object Model. For example, the first clip in the third track can be accessed by the path
As you can see, different paths can point to the same Live object. Only one of these paths is the canonical path (see below).
When communicating with the Live API, no quotes are used in paths. List indexes start with 0.
When navigating through the object model, besides these absolute paths, relative paths can be used. These determine a subpath beginning at the current position in the object hierarchy.
(Absolute) paths to all objects start with one of
: allows you to access controls of the Live application itself. This can be useful if you want to toggle the browser view, zoom or scroll features in Live.
: allows you to access various parameters within Live, for example Track Volume, Clip parameters (including launching Clips), etc.
: allows you to access various control surface features (depending on your controller).
: allows you to construct API paths relative to the device you are in.
Different paths can lead to the same object.
Each object has a unique canonical path, in this case. The canonical path is sent out of live.object in reponse to . In the Live Object Model, the canonical path is shown by bold connectors.
Additionally to what is described in the LOM, all objects have achild which is used by Live to determine the canonical path of an object. The canonical parents are get-only and useful for patching, too. For example, is the perfect way to get the own track object.
An object id identifies a particular object instance in Live like a track or a clip.
To get an id, a live.path object must be used to navigate to the Live object. When a live.path object sees this Live object the first time, an id is assigned to it.
The id is only valid inside the device with the live.path and remains unchanged as long the object exists. If the object is moved in Live, its id usually remains unchanged. There may be exceptions if the movement is implemented as a delete/create sequence, though. When an object is deleted and a new object is created at its place, it will get a new id.
An id is never reused in the scope of a Max device. Ids are not stored. Therefore, after loading a saved device, the live.path object must navigate to the object again.
An object id consists of the word and a number, separated by a space, like . refers to no object. In Max terms it's a list of the symbol and an integer.
Each Live object is of a particular object type (or class), like
When live.object refers to a Live object, sending it will send all the Live object's children, properties and functions to its left outlet.
Live objects have children identified by name. Some names, like
List names are in plural, whereas single child names are in singular. Lists may be empty. Sending to live.path allows to find out how many children are in the list.
Single children names may point to no object, in which case you get if you navigate there or send to live.object.
Most children can be monitored using live.observer.
Live objects have properties which describe its actual state. Properties are accessed by sending live.object. Not all properties can be set, though.
Many properties can be monitored using live.observer.
Many Live objects have functions which can be called by sending live.object, like for a object. A function call may have parameters (a list of values). The return value will be sent out from the outlet of live.object.and the function name to
Properties and function parameters or return values used in the Live Object Model and by the Max objects to access the Live API have one of the following data types:
|bool||0 for false and 1 for true|
a string with unicode character set
Use double quotes in message boxes to create symbols with spaces:
Double quotes in symbols are to be prefixed by backslashes:
Backslashes are to be included as double backslashes: creates the symbol .
|int||a 32 bit signed integer|
|float||a 32 bit float value|
|double||a 64 bit float value (maily used for timing values)|
|beats||song beat time counted in quarter notes, represented as double|
song time in seconds, represented as double
Time is given in seconds: , or sometimes in milliseconds:
|list||a space separated list of the types above|
When Max devices need to know the state of the Live application and its objects, they can actively poll the state by navigating through the object hierarchy and getting object properties or calling functions.
But changes happen in Live while the Max device is passive. To allow the Max device to react on these changes in Live, notifications are sent from Live to the Max device. Notifications are spontaneous in the sense that messages are sent to outlets spontaneously, not in response to a message received at an inlet.
The notifications include object ids sent when the Live object at a certain path changes and values sent when a property changes.
Note: changes to a Live Set and its contents are not possible from a notification. The error message in the Max Console is 'Changes cannot betriggered by notifications'. In many cases putting a deferlow between the notification outlet and the actual change helps to resolve the issue.
Four Max objects interact in a certain way to allow Max devices to access the Live objects.
|live.path||select objects in the Live object hierarchy|
|live.object||get and set properties and children, call functions|
|live.observer||monitor properties and children|
|live.remote~||control Live device parameters in real time|
The following patch shows the typical interconnections between the Live API objects. live.path is sending object ids out of its leftmost outlet connected to the rightmost inlet of live.object, live.observer and live.remote~. This causes these objects to operate on the object selected by live.path.
live.path objects are used to navigate to the Live objects on which live.object, live.observer and live.remote~ are supposed to operate. For this purpose, navigation messages like are sent to live.path, which replies by sending an object id to the left outlet.
live.path can also observe the given path, and when the object at this path changes, its id is sent to the middle outlet. This is particularly useful for paths like which point to the currently selected track.
live.observer monitors the state of a particular Live object which id has been received from live.path. After telling live.observer which property to observe it recognizes all changes of the property and sends the current values to its left outlet.
live.remote~ receives the id of a DeviceParameter object from live.path and then allows to feed this parameter with new values by sending them into the left inlet, in realtime, without effects on the undo history or the parameter automation, which is deactivated.
DeviceParameter objects are children of Live devices, including Max devices, and also of tracks, like volume and pan.
Here are some examples of accessing Live from Max.
Controlling the volume slider of the selected track
Getting the volume of a track
To get the volume of a track in Live, we first need to find the path to the volume parameter of the track's mixer device.
In the Live Object Model reference, the graph can be navigated starting at the root node. From the object, we use to get the list of children. We select the second track with (note that indexing starts at 0). We then use to get its object, and finally by using , we get to the volume object.
We can now send this path to a live.path with the following message: . live.path will give us back (where n is an integer), which represents the object we need. It gives us access to the properties of the mixer device's volume control, like its range ( and ), default value ( ) or current value ( ).
When we send this id to the right inlet of a live.object, we can get the properties of the DeviceParameter object with messages. By sending to the live.object, it will send the current volume value to its left outlet as a number between 0 and 1.
Initializing a path when the device loads
If we want to make sure the live.object is set to the path we specified as soon as the device is loaded, we might be tempted to use loadbang to send the message to live.path. It is important to know that we need to use live.thisdevice instead, to make sure the Live API is initialized before interacting with it.
Getting the volume of the selected track
In the previous example we hard-coded getting the volume value of the second track. However, if we would like to get the value of the selected track, we can use the
After finding the keyword in the Live Object Model reference, we see that it is a child of . In the graph we see that the can be reached from the object type with the keyword. So we send the following message to live.path: . This will send the id of the currently selected track to the left outlet, which we send to live.object.
Knowing when a different track is selected
In the previous example, we got the id of the selected track once. However, if we select a different track, this id is no longer up to date. If we want the id from a path containing a dynamic element like live.path.
Hovering the mouse cursor over the outlets over an object will show you what they send out. The second outlet of live.path reads . When instead of the live.path's left outlet we connect its second outlet to live.object, the live.object will be kept up to date, even after selecting a different track.
There is one catch, as mentioned under Notifications. Since the second outlet of live.path sends us notifications from Live, when we connect it to another Live API object like live.object, we need to add a deferlow in-between to make sure the next API interaction is not attempted before the first is finished.
Setting the volume of a track
In much the same way as getting the current volume of a track like above, we can also change the value of a volume fader.
We can add a slider with a range between 0 and 1, connected to a message box saying . We can then connect this to the live.object as set up above, and now our slider will control the volume slider in Live.
Observing the volume of a track
We might want to get an update in our device whenever a Live user changes a volume slider. For this, we can send the id from the previously set up live.path to a live.observer that has its argument set to the property . Now, the up to date volume values will be output from the live.observer's left outlet.
Finally, we can set this value to the slider we created earlier. We now have a device with a slider that mimics and changes the volume slider of the selected track in Live.
Triggering a clip with MIDI notes
Navigating to a specific clip and triggering it
Apart from children and properties, Live objects also have functions. Looking at the LOM reference, under , in the Functions section, we can find the function. To call this function, we first need to refer a live.object to the clip we want to launch. For this, we need the clip's id.
Getting an id is done with live.path. Finding out what path to supply is most easily done by looking at the LOM graph. In the graph, we find the object. To reach it, we start at the Song root node ( ), go to its list of children and pick the first ( ). Next we go to the list of children and pick, for example, the fourth ( ), and finally we navigate to the contained by this clip slot ( ). So the message we send to live.path will be .
We send the id output from the left outlet of live.path to live.object's second inlet. There are no dynamic elements in the path, so we don't need to use live.path's second outlet. And now that we are ready to launch the clip, we simply send to the left inlet of the live.object.
Adding control of which clip to fire and checking if it exists
We might want to use two live.numboxes to control the track number and the clip slot number that we want to launch. The outputs of the numboxes can be sent to pak and we can swap the hardcoded numbers in the path above with replaceable arguments: .
Of course, with this approach, the user of this device will be able to select tracks or clip slots that don't exist in the Live set. To show a toggle that is on when the selection exists and off otherwise, we can use that is output for paths that don't exist.
Finally, to make this a functional device, we can place this patch in a MIDI effect and use notein to trigger the selected clip. If the velocity is not 0, we know a note on comes in. So then, if the selected clip exists, we send to it.
|Max For Live||Max For Live|
|Live Object Model||LOM - The Live Object Model|
|live.path||Navigate to objects in the Live application|
|live.object||Perform operations on Live objects|
|live.observer||Monitor changes in Live objects|
|live.remote~||Realtime control of device parameters|
|Using the Live API||Creating Devices that use the Live API|