15 Routing and I/O

In the context of Live, “routing“ is the setup of the tracks’ signal sources and
destinations (i.e., their inputs and outputs). Most routing happens in the mixer’s track
In/Out section, which offers, for every track, choosers to select a signal source and
destination. The mixer’s In/Out section is Live’s “patchbay.“

The Mixer’s In/Out Section.

You can show or hide the I/O section of the mixer in either Session or Arrangement
View using the In/Out entry in the mixer’s view control menu at the bottom right
corner of Live’s window, or via the View menu’s In/Out option in the Mixer Controls
submenu, or using the shortcut [CTRL][ALT][I] (Win) / [CMD][ALT][I] (Mac).
 The Mixer View Control’s Options Menu.

For every track that can play clips, the In/Out section has the same layout:

• The upper chooser pair (“Audio/MIDI From“) selects the track’s input. Audio
tracks have an audio input, and MIDI tracks have a MIDI input. Return tracks
receive their input from the respective sends (see ‘Return Tracks and the Main
track’).
• The Monitor radio button selects the monitor mode: the conditions under
which the track’s input is heard through the track.
• The lower chooser pair (“Audio/MIDI To“) selects the track’s output. All tracks
have audio outputs, except for MIDI tracks without instruments. Remember
that instruments convert MIDI to audio (see ‘Devices and the Mixer’).

Within a chooser pair, the upper chooser selects the signal category (“Ext.,“ for
instance, for external connections via an audio or MIDI interface), and is called the
Input/Output Type chooser. If this signal type offers sub-selections or channels, they
are available from the lower chooser, or the Input/Output Channel chooser. In our
“Ext.“ example, these would be the individual audio/MIDI inputs and outputs.

15.1 Monitoring
“Monitoring,“ in the context of Live, means passing a track’s input signal on to the
track’s output. Suppose you have set up an audio track to receive its input signal from
a guitar. Monitoring then means that the signal from your live guitar playing actually
reaches the track’s output, via the track’s device chain. If the track’s output is set to
“Main,“ you can hear the guitar signal, processed by whatever effects are used (and
delayed by whatever latency the audio hardware interface incurs), over your speakers.

The In/Out section offers, for every audio track and MIDI track, a Monitor radio button
with the following three options:

• The default Auto-monitoring setting does the right thing for most
straightforward recording applications: Monitoring is on when the track is
armed (record-enabled) (see ‘Recording New Clips’), but monitoring is
inhibited as long as the track is playing clips.
• To permanently monitor the track’s input, regardless of whether the track is
armed or clips are playing, choose In. This setting effectively turns the track
into what is called an “Aux“ on some systems: the track is not used for
recording but for bringing in a signal from elsewhere. With this setting, output
from the clips is suppressed. An “In“ monitoring setting can be easily
recognized even when the In/Out section is hidden by the blue color of the
track’s Activator switch.
 • Monitoring can be turned off altogether by choosing the Off option. This is
useful when recording acoustic instruments which are monitored “through the
air,“ when using an external mixing console for monitoring or when using an
audio hardware interface with a “direct monitoring“ option that bypasses the
computer so as to avoid latency. Generally, it is preferable to work with an
audio interface that allows for negligible latencies (a few milliseconds). If you
are recording into Live with monitoring set to “Off,“ you may want to make
the Audio Preferences’ Overall Latency adjustment, which is described in the
built-in program tutorial on setting up the Audio Preferences.

When monitoring is set to “In” or “Auto,” the “Keep Monitoring Latency in Recorded
Audio” option will be enabled by default. This adjusts the timing of the recording to
match what is heard through Live’s monitoring. Generally speaking it is
recommended to leave this option enabled when recording software instruments or
effects, and to switch it off when recording acoustic instruments or relying on external
monitoring. You can right-click on the “In” or “Auto” monitor buttons to manually
switch “Keep Monitoring Latency in Record Audio” on or off.

If multiple tracks are selected, pressing one of the Monitor buttons applies this
selection to all of the selected tracks.

The Monitor buttons can also be restored to their default state. When the In/Out
section is expanded, you can press the Delete key to reset the Monitor buttons to the
default (“Off” for audio tracks and “Auto” for MIDI tracks), or you can select the Edit
menu option “Return to Default.”

15.2 External Audio In/Out

An audio interface’s inputs are selected by choosing “Ext. In“ from the Input Type
chooser of an audio track. The Input Channel chooser then offers the individual input
channels. Entries in this chooser each have meters next to their names to help you
identify signal presence and overload (when the meter flashes red). Setting up the
audio interface’s outputs works the same way via the output chooser pair. If multiple
tracks are selected, any changes you make to these choosers will be applied to all
selected tracks.

The list of available inputs and outputs depends on the Audio Preferences, which can
be reached via the Input and Output Channel choosers’ “Configure…“ option. Note
that the Audio Preferences also provide access to the Channel Configuration dialogs,
which determine which inputs and outputs are used, and whether they are available
to Live as mono or stereo pairs. Essentially, the Channel Configuration dialog tells
Live what it needs to know about how the computer is connected to the other audio
components in your studio.
You can rename any input and output channels that appear in the Channel
Configuration dialogs. If changed, the new name(s) will be displayed in the
corresponding Input / Output Channel chooser drop-down. You can rename channels
more quickly by using the [Tab] key to move between them. Note that changed
names are always associated with their respective audio device.

15.2.1 Mono/Stereo Conversions

When a mono signal is chosen as an audio track’s input, the track will record mono
samples; otherwise it will record stereo samples. Signals in the track’s device chain
are always stereo, even when the track’s input is mono or when the track plays mono
samples.

Mono is turned into stereo simply by using the identical signal for left and right
channels. When a track is routed into a mono output, the left and right signals are
added together and attenuated by 6 dB to avoid clipping.

15.3 External MIDI In/Out

MIDI from the outside world is routed into Live just like audio. From the Input Type
chooser of a MIDI track, you can either select a specific MIDI input port or “All Ins,“
which is the merged input of all external MIDI ports. The Input Channel chooser offers
the individual input channels of the selected MIDI port and the merged signal of all
channels, “All Channels.“ As is the case with audio inputs, the Input Channel chooser
also has meters next to every entry to represent activity on the respective input
channel. If multiple MIDI tracks are selected, any changes you make to these choosers
will be applied to all selected tracks.

15.3.1 MIDI Port Inputs and Outputs

You can configure which MIDI ports are made available to Live using
the Inputs and Outputs options in the MIDI section of the Link, Tempo & MIDI
Preferences. All available input and output ports are listed here. You can use any
number of MIDI ports for track input and output; the mixer’s In/Out choosers allow
them to be addressed individually.

The MIDI Port Inputs and Outputs List in the Preferences.

15.3.1.1 Track
Enabling Track allows Live to send or receive note and CC (control change) messages,
for example, when using a MIDI keyboard to play or enter pitches.

Activate Track for a MIDI port’s input when: - Playing instruments in Live with a MIDI
keyboard. - Recording notes into MIDI clips. - Recording MIDI CC messages into MIDI
clips, for example to capture parameter changes from an external hardware
synthesizer.

Activate Track for a MIDI port’s output when: - Triggering an external hardware device
(like a synthesizer, drum machine, etc). - Sending MIDI notes to another application
(using a virtual MIDI bus). - Sending MIDI CC automation to an external device or
application.

Note: You only need to activate Track on the output port for a MIDI controller if it has
a built-in sound generator.

15.3.1.2 Sync
Sync allows Live to send or receive MIDI Clock, or receive MIDI Timecode. Note:
Unless it has a built in sequencer or arpeggiator, you won’t ever need to activate Sync
on the input or output ports of a MIDI controller.

Activate Sync for a MIDI port’s input when: - Synchronizing Live to an external
sequencer, drum machine or groove box. - Synchronizing Live to another DAW using
MIDI.

Activate Sync for a MIDI port’s output when: - Synchronizing an external sequencer,
drum machine or groove box to Live using MIDI Clock. - Synchronizing another DAW
to Live using MIDI Clock. - Synchronizing the LFO and arpeggiator of an external
synthesizer or MIDI controller to Live.

When Sync is enabled for a port’s output, you can access a set of additional options
by pressing the triangle next to the port’s name.
 Sync Output Options.

You can adjust the MIDI Clock Sync Delay amount to add a delay to outgoing MIDI
sync signals in milliseconds. This can help correct any timing issues that occur
between Live and the external hardware.

MIDI Clock Type can be set to either Song to Pattern. In Song Mode, Live will send
out MIDI Song Position Pointer (SPP) and Continue messages each time the play
position changes. In Pattern Mode, Live will only use Start messages, sent out at the
start of the following bar. Use Pattern Mode if your MIDI device does not recognize
SPP messages.

The Hardware Resync drop-down lets you choose how a resync message is sent when
the Resync External Hardware option is enabled.

Resync External Hardware Option.

When enabled, the Resync External Hardware button appears in Live’s Control bar,
and can be used to send resync messages out to external gear. This is useful when
synced hardware drifts out of time with the Live Set during playback.
 The Resync External Hardware Button in the Control Bar.

The default behavior is Stop and Start, which sends a resync message consisting of a
MIDI Clock Stop event followed by a MIDI Clock Start event; this works best with most
MIDI devices. If set to Start Only, just the MIDI Clock Start event resync message is
sent; this might work better for some devices. If set to Don’t Resync, no resync
messages are sent.

15.3.1.3 Remote
The Remote switch allows you to create mappings from a MIDI controller to
parameters in Live or to send feedback to a MIDI controller.

Activate Remote for a MIDI port’s input when: - Creating custom MIDI mappings to
be able to control parameters in Live. - Using a MIDI keyboard to trigger MIDI Clips.

Activate Remote for a MIDI port’s output when: - Using MIDI controllers with LED’s
that reflect the status of mapped Live parameters. - Using MIDI controllers with
motorized faders that reflect the status of mapped Live parameters.

15.3.2 Playing MIDI With the Computer Keyboard

The computer keyboard can be used for generating MIDI notes from computer
keyboard strokes. To turn the computer MIDI keyboard on, activate the Control Bar’s
Computer MIDI Keyboard button, or enable the “Computer MIDI Keyboard” entry in
the Options menu, or use the [M] shortcut.

Activating the Computer MIDI Keyboard.

The center row of letter keys on the keyboard will play notes corresponding to the
white keys on a piano, beginning on the left with the note C3. The black keys on a
piano correspond to the upper row of computer keys. The four leftmost letters on the
lower row of the keyboard (Z,X,C, and V on a U.S.-English keyboard) are used to
transpose the note range and to set velocity, as follows:

• The leftmost keys (Z and X) adjust the keyboard’s octave range.

• The next two keys (C and V) adjust incoming note velocity by intervals of twenty
(20, 40, 60, and so on).
When the computer keyboard is set to send notes between C3 and C4, the keys are
mapped to MIDI notes in such a way that the center row of the keyboard (ASDF…),
corresponds to the Impulse percussion sampler’s sample slots (see ‘Impulse’). This
means that you can play and record drum patterns directly from the computer
keyboard.

Note that when the computer MIDI keyboard is activated, it will “steal“ keys that may
have otherwise been assigned to remote-control (see ‘Computer Keyboard Remote
Control’) elements of the Live interface. To prevent this, you can turn the computer
MIDI keyboard off when it is not needed. Additionally, shortcuts that use single
letters, such as [S] for soloing tracks, can be accessed when the Computer MIDI
Keyboard is enabled by adding [Shift], e.g., [Shift][S].

15.3.3 Connecting External Synthesizers

Routing MIDI to an external synthesizer is straightforward: The Output Type chooser
is set to whatever MIDI port the synthesizer is connected to; the Output Channel
chooser is used to select which MIDI channel to send on.

In addition to routing via a track’s In/Out section, it is also possible to route from
within a track’s device chain by using the External Instrument device (see ‘External
Instrument’). In this case, you can send MIDI out to the external synthesizer and return
its audio — all within a single track.

Important: If you are using a keyboard synthesizer both as a master keyboard to play
into Live and as a sound generator, then please make sure to check the synthesizer’s
“Local Off“ function. Every synthesizer has this function, which effectively separates
the keyboard from the sound generator, allowing you to treat both components as if
they were separate devices. This allows you to use Live as the hub of your MIDI studio,
which receives MIDI from the keyboard and dispatches the incoming MIDI, as well as
the MIDI from the clips, as appropriate.

15.3.4 MIDI In/Out Indicators

Live’s Control Bar contains three pairs of indicator LEDs that tell you about incoming
and outgoing MIDI. These indicators tell you not only about the presence of signals,
but also about their use. In every pair, the upper indicator flashes when a MIDI
message is received, and the lower indicator flashes when a MIDI message is sent.

The Control Bar’s MIDI Indicators.

The three indicator pairs represent, from left to right:

 1. MIDI Clock and Timecode signals that are used for synchronizing Live with
other sequencers (see ‘Synchronizing with Link, Tempo Follower, and
MIDI’). Note that this set of indicators is only visible when an external sync
source has been enabled for a MIDI port in the Link, Tempo & MIDI
Preferences;
2. MIDI messages that are used for remote-controlling Live’s user-interface
elements (see ‘MIDI and Key Remote Control’);
3. MIDI messages coming from and going to Live’s MIDI tracks.

MIDI messages that are mapped to remote-control Live’s user-interface elements are
“eaten up“ by the remote control assignment and will not be passed on to the MIDI
tracks. This is a common cause of confusion that can be easily resolved by looking at
the indicators.

15.4 Resampling
Live’s Main output can be routed into an individual audio track and recorded, or
resampled. Resampling can be a fun and useful tool, as it lets you create samples
from what is currently happening in a Live Set that can then be immediately
integrated. It can be used to record tracks that include processor-intensive devices,
so as to delete the devices, or for quickly previewing before rendering to disk
(see ‘Exporting Audio and Video’).

The “Resampling“ option in any audio track’s Input Type chooser will route the Main
output to that track. You can then decide on what exactly you will be resampling and
mute, solo or otherwise adjust the tracks that are feeding the Main output. You will
probably want to use the Main Volume meter to make sure that your level is as high
as possible without clipping (indicated by red in the meter). Then you can arm the
track and record into any of its empty clip slots (see ‘Recording Into Session Slots’).
Note that the recording track’s own output will be suppressed while resampling is
taking place, and will not be included in the recording.

Samples created by resampling will be stored in with the current Set’s Project folder
(see ‘Live Projects’), under Samples/Recorded. Until the Set is saved, they remain at
the location specified by the Temporary Folder (see ‘Where are the Recorded
Samples?’).

15.5 Internal Routings

Live’s mixer and external routing devices allow for inter-track routings. These routings,
albeit potentially confusing, enable many valuable creative and technical options. Via
the mixer, inter-track routing can work two ways:
 1. Track A is set up to send its output signal to Track B. This is possible
because every track that can receive an output signal of the appropriate
type from Track A shows up in its Output Type chooser.
2. Track B is set up to receive its input signal from Track A. This works because
every track that delivers a signal of the appropriate type appears in Track
B’s Input Type chooser.

Two Ways to Route Track A into Track B.

Both approaches result in Track A’s output being fed into Track B. Approach 1 leaves
Track B’s in/out settings alone, and we can, at any time, add more tracks that feed
their output into Track B. This is the method of choice for “many-to-one“ routings
such as submixes or several MIDI tracks playing the same instrument. In this scenario,
soloing Track B will still allow you to hear the output of the tracks that are feeding it.
Also, you can still solo Track A and hear its output signal. In this case, all other tracks
are muted, including those that might also feed into Track B. Technically, what you
hear is the output of Track B, with everything except Track A’s signal removed.

Approach 2, on the other hand, leaves Track A unaffected except for Track B tapping
its output. We can easily add more tracks like Track B that all tap Track A’s output.
Instrument layering is a good example of such a “one-to-many“ routing setup.

15.5.1 Internal Routing Points

Signals travel from Live’s tracks into their respective device chains and then into the
track mixer, where they might become panned or have their levels altered by the
tracks’ faders.

Whenever a track’s Audio From input chooser is set to another track (as described in
the previous section’s Approach 2), the signal received can be tapped from one of
three different points chosen from the Input Channel chooser: Pre FX, Post FX or Post
Mixer.
 Tap Points for Track Routing.

• Pre FX taps the signal that is coming directly from a track, before it has been
passed on to the track’s device chains (FX) or mixer. Therefore, changes that
are made to the tapped track’s devices or mixer have no effect on the tapped
signal. Soloing a track that taps another track Pre FX will allow you to hear the
tapped track.
• Post FX taps the signal at the output of a track’s device chains (FX), but before
it has been passed back to the track mixer. Changes to the tapped track’s
devices will therefore alter the tapped signal, but changes to its mixer settings
will not. Soloing a track that taps another track Post FX will allow you to hear
the tapped track.
• Post Mixer taps the final output of a track, after it has passed through its device
chains and mixer. Soloing a track that taps another track Post Mixer
will not allow you to hear the tapped track.
15.5.1.1 Routing Points in Racks

Tap Points for Every Chain in a Track.

If a track has one or more Instrument or Effect Racks (see ‘Instrument, Drum and Effect
Racks’) in its device chain, internal routing points (Pre FX, Post FX and Post Mixer) will
also be available for every chain within the Rack. If a track contains one or more Drum
Racks (see ‘Drum Racks’), internal routing points will be available for any of the Rack’s
return chains. Each Rack will also be listed in the Input Channel chooser:

• (Rack Name) | (Chain Name) | Pre FX — The signal will be tapped from the
point that it enters the Rack, before it reaches the chain’s devices.
 • (Rack Name) | (Chain Name) | Post FX — The signal will be tapped from the
end of the chain, but before it passes to the chain’s mixer.
• (Rack Name) | (Chain Name) | Post Mixer — The signal will be tapped from the
output of the chain’s mixer, just before the point where all of the chains in the
Rack are summed together to create the Rack’s output.

Soloing a track that taps a Chain at any of these points will still allow you to hear the
output at that point.

15.5.2 Making Use of Internal Routing

This section presents several internal routing examples in more detail.

15.5.2.1 Post-Effects Recording

Let’s say that you are feeding a guitar into Live, building up a song track by track,
overlaying take onto take. It is certainly powerful to have a separate effects chain per
track for applying different effects to different takes — after the fact. You might,
however, want to run the guitar signal through effects (a noise gate or an amp model,
for instance) before the recording stage, and record the post-effects signal.
 An Example Setup for Post-Effects Recording.

This is easily accomplished by devoting a special audio track for processing and
monitoring the incoming guitar signal. We call this track “Guitar“ and drag the
desired effects into its device chain. We do not record directly into the Guitar track;
instead we create a couple more tracks to use for recording. Those tracks are all set
up to receive their input Post FX from the Guitar track. Note that we could also tap
the Guitar track Post Mixer if we wished to record any level or panning from it.

As for monitoring, we set the Guitar track’s Monitor radio button to In, because we
always want to listen to our guitar through this track, no matter what else is going on
in Live. The other tracks’ Monitor radio buttons are set to Off.

15.5.2.2 Recording MIDI as Audio

When working with MIDI and complex software instruments, it is sometimes more
useful to record the resulting audio than the incoming MIDI. A single MIDI note can
prompt, for example, Native Instruments’ Absynth to produce something that sounds
more like a piece of music than a single tone. This output lends itself more to
representation as an audio waveform than a single note in a MIDI clip, particularly
when comparing the editing options.
 Recording the Output of a Complex Instrument in Audio Tracks.

A setup similar to the one described above (see ‘Post-Effects Recording’)

accomplishes the task. We have one MIDI track hosting the virtual instrument, and we
use an additional audio track to record the audio result as the instrument is played.

15.5.2.3 Creating Submixes

 Submixing the Individual Drums of a Drum Kit.

Suppose we have the individual drums of a drum kit coming in on separate tracks for
multitrack recording. In the mix, we can easily change the volumes of the individual
drums, but adjusting the volume of the entire drum kit against the rest of the music
is less convenient. Therefore, we add a new audio track to submix the drums. The
individual drum tracks are all set to output to the submix track, which outputs to the
Main track. The submix track gives us a handy volume control for the entire drum kit.

Alternatively, you could combine the separate drum tracks into a Group Track
(see ‘Group Tracks’) for even more flexibility. This automatically creates the necessary
output routings and also allows you to hide or show the component tracks.
 Submixing by setting a track’s Output Type to Sends Only

A third possibility is to use Live’s return tracks for submixing. This is done by selecting
the Sends Only option in a track’s Output Type, then turning up a Send control as
desired. The corresponding return track will then act as a submixer channel.

15.5.2.4 Several MIDI Tracks Playing the Same Instrument

Consider a MIDI track containing a virtual instrument — a Simpler playing a pad
sound, for example. We have already recorded MIDI clips into this track when we
realize that we would like to add an independent, parallel take for the same
instrument. So we add another MIDI track. We could now drag another Simpler into
the new track, but we would really like to reuse the Simpler from the pad track, so
that changing the pad’s sound affects the notes from both tracks.
 Feeding an Additional MIDI Track Into an Existing MIDI Track to Reuse its Instrument.

This is accomplished by setting the new MIDI track’s Output Type chooser to the pad
track. Note that the Output Channel chooser now offers a selection of destinations:
We can either feed the new track’s output into the input of the pad track, or we can
directly address the Simpler. The “Track In“ option in the Output Channel represents
the pad track’s input signal (the signal to be recorded), which is not what we want.
We instead select “Warm Bubbly Pad“ to send the new track’s MIDI directly to the
Simpler, bypassing the recording and monitoring stage. With this setup, we can
choose to record new takes on either track and they will all play the same pad sound.

The Instrument Has Been Isolated in a Dedicated Track.

We might be bothered by the fact that muting the pad track (by turning off its
Activator switch) also mutes the other MIDI track. To be precise, the other track keeps
playing, but its MIDI is played by an instrument that is out of the mix. This can be
easily remedied by cutting the clips from the pad track and pasting them into a third
track that can be independently muted (and that can hold its own MIDI effects). The
original pad track now acts as a mere instrument container. As we are not recording
new clips into this track, we can set its Input Type chooser to “No Input,“ which makes
its Arm button disappear and helps to avoid confusion when the mixer’s In/Out
section is hidden.

15.5.2.5 Tapping Individual Outs From an Instrument

Some software instruments, like Live’s Impulse percussion sampler, offer multiple
audio outputs for the signals they produce. By default, Impulse mixes the output of
its eight sample slots internally and delivers the mix at the instrument’s audio out.
Any audio effects following Impulse in the same track process the composite signal.
Sometimes it is desirable to take an individual drum sound out of the mix for individual
effects processing and mixing. This is possible because Impulse offers its sample slots
as audio sources to other tracks.

Using Impulse’s Individual Outs to Separately Process Sample Slots.

We simply create an audio track and select from its Input Type chooser the track with
the Impulse. The Input Channel chooser now offers, in addition to Pre FX, Post FX
and Post Mixer, Impulse’s eight individual outputs, labeled according to the sample
used in each slot. Notice that routing an individual output from Impulse into another
track automatically takes this signal out of Impulse’s own internal mix. This
convenience is not standard behavior of most plug-in instruments, however. Soloing
a track that taps one of Impulse’s sample slots will still allow you to hear the output
of that slot.

15.5.2.6 Using Multi-Timbral Plug-In Instruments

Many plug-in instruments support multi-timbral operation. A multi-timbral instrument
is like several instruments in one, with each component “part“ (or whatever term the
manufacturer uses) receiving MIDI on a separate MIDI channel. Usually, the multi-
timbral instrument offers individual outputs so that the parts can be separately routed
into the mixer. Or, the instrument might offer a submixer of its own.

Tracks Feeding MIDI to and Tapping Audio From the Parts of a Multi-Timbral Instrument.

Sending MIDI from the mixer to a multi-timbral instrument is a variation of a case

described above (see ‘Several MIDI Tracks Playing the Same Instrument’). One MIDI
track hosts the multi-timbral instrument, and additional MIDI tracks are used to feed
its individual parts. Each additional MIDI track has its Output Type chooser pointed
to the track that contains the instrument, and its Output Channel chooser referencing
the target MIDI channel. Additional audio tracks can then be used to tap the
instrument’s individual outputs, as described earlier (see ‘Tapping Individual Outs
From an Instrument’).

It is also possible to use the External Instrument device to route MIDI to (and audio
from) the secondary outputs on multi-timbral plug-ins. This scenario eliminates the
need to create an additional audio track for each tapped output:

1. Insert the multi-timbral instrument on a MIDI track.

2. Insert an External Instrument device on another MIDI track.
3. Select the track that contains the instrument in the first MIDI To chooser on
the External Instrument device.
4. Select the MIDI channel to route to in the second chooser on the External
Instrument device.
5. From the External Instrument’s Audio From chooser, select a secondary
output on the instrument to which you are sending MIDI.

Repeat steps 2-5 to feed and tap additional components of your multi-timbral
instrument. You could also put the entire system of External Instrument devices into
a single track, by placing each one in a Rack’s device chain.

Note that the main outputs of the multi-timbral instrument will still output to the track
that contains the instrument — only auxiliary outputs are available to the External
Instrument device.

15.5.2.7 Feeding Sidechain Inputs

Some effects have so-called “sidechain inputs.“ A vocoder, for instance, imposes
spectral characteristics taken from one signal (say, spoken word) onto another signal,
for instance a string pad. The vocoder is inserted as an audio effect into the string
track. It has a sidechain input for the speech signal, which has to be delivered from
another track. So, we create an additional audio track named “Speech“ and set its
Output Type chooser to the “Strings“ track. From the Output Channel chooser, we
select the vocoder’s sidechain input.

Some vocoder plug-ins include a built-in synthesizer to generate the “carrier“ signal.
In this case, the only difference from the above procedure is that the vocoder
instrument is dragged into a MIDI track. Feeding the sidechain audio input works as
described above.

A number of Ableton’s built-in devices have their own sidechain controls with
integrated routing choosers that match those found in tracks. Thus when using these
devices, it is not necessary to follow the above procedure — you can simply select
the sidechain source from within the device itself.
15.5.2.8 Layering Instruments
Suppose that we have a MIDI track containing an instrument playing a string sound,
which we would like to augment by adding a brass sound playing the same notes.
This can be easily done by adding a MIDI track that contains an instrument playing
the brass sound and setting its Input Type chooser to tap the string track’s Post FX
signal.

Using an Auxiliary MIDI Track to Layer Instruments.

Perhaps you wonder why this works, given that the string track’s output is audio and
not MIDI. When routing MIDI in from another track, we are tapping the MIDI at the
latest possible stage, which is after any MIDI Effects, and just before the instrument.