AUM Users Guide


Also see Frequently Asked Questions at the AUM website.


AUM is a flexible audio mixer, plugin host, and recorder.

Channel strips

The basic building block is the channel strip. They come in two flavors, Audio strips for processing audio, and MIDI strips for hosting non-audio nodes such as MIDI sequencer plugins.

A channel strip has nodes (see below) that represents inputs, outputs and effects in audio strips, or MIDI plugins in midi strips. Audio strips also have a level fader, mute and solo buttons, and a record-enable button.

Creating channels

Create a channel by tapping the big square plus-button and selecting Audio or MIDI. Tap again to create yet another channel, etc.

Rename or delete a channel

At the bottom of the channel is the channel title. Tap it to rename or delete the channel. If the channel has no specified name, it will automatically be named "CHAN N", or "ChN: SOURCE" where N is the number of the channel and SOURCE is the title of the input node of the channel.

Reorder channels

You can reorder a channel by dragging its title label upwards and keep holding while moving your finger left or right. The order of the channels has only visual meaning, and does not affect the signal path in any way. (Except for the special case of feedback routings, where the order will affect at which node the feedback happens).

MIDI strips are always processed before any audio strips, regardless of the visual order.

Bookmark channels

You can bookmark channels to quickly jump to one later. This is useful if you have a large project where you need to scroll to see all channels.

Tap a channel's title, then toggle the bookmark button in the top right of the view that shows up. The channel will now be listed in the bookmarks menu, available by tapping the bookmark symbol at the lower right corner of the main screen.

Duplicating channels

You can duplicate channel strips by tapping the channel title label and then the DUPLICATE button.

All the nodes in the channel strip, including their state and MIDI control mappings, will be duplicated and appended as a new channel strip in the session.

Importing channels

You can import one or several channels from other sessions and append them to your current session. This is useful as a way to create reusable channel templates that you can use in multiple projects.

Tap the big square plus-button and select "IMPORT", then choose from which session you want to import channels. Alternatively, long-press a session file in the FILES menu and choose "Import channels". After that, you'll be able to select which specific channels to import.


Each audio strip have slots to hold an input source, one or more optional effect inserts, and an output destination. MIDI strips have one or more MIDI slots to hold MIDI plugins that don't process or generate any audio. The things you can put in a slot are called nodes.

Loading nodes

Tap the plus-sign in an empty slot to load a node into the slot. This will open the node-picker, listing the available nodes for this kind of slot.

Drag down to reveal a search bar where you can easily find specific nodes or plugins.

Eject a node

To remove a node, swipe it to the left to reveal the eject button. In this state, the node is bypassed. Tap the eject button to remove the node.

Adding more effect or MIDI slots

The area for the effect insert slots is scrollable, the same goes for the slots in a MIDI strip.

To add more slots, scroll to the bottom and tap the circled "+1" button.

You can also double-tap on the empty area below the current slots to quickly add another one.

Pre/post fader

In audio strips, the wire line going between the level fader and the effect insert chain shows which inserts are pre and post fader.

Pre-fader inserts will get the full level of the previous node, while post-fader inserts will have their input level controlled by the level fader.

Long-press an effect insert slot to bring up the pre/post menu, where you can change at which point in the chain the level fader is connected.

Reorder effect and MIDI nodes

You can reorder effects and MIDI nodes by dragging it right and keep holding while moving your finger up or down. The order of the effect nodes determine their position in the signal chain, and can thus affect the sound. The order of the MIDI nodes have only visual meaning. Reordering is not possible while the pre-post option is open.

Deleting slots

To delete an empty effect or MIDI slot, tap it and scroll down to reveal the "REMOVE EMPTY SLOT" button. There must be at least 2 slots in a strip for this button to show up.

Signal routing

AUM offers very flexible routing, and supports multi-channel audio interfaces, internal busses for grouping, submixing and effect sends, as well as multiple Inter-App Audio output ports.

Hardware inputs / outputs

Tap an empty input slot and choose "Hardware Input" to show a list of available hardware inputs.

Tap an empty output slot and choose "Hardware Output" to show a list of available hardware outputs.

External audio interfaces will also show up here, including all their channels.

Hardware channels are available as both stereo pairs and individual mono channels.

Tap an item in the list to load it into the slot.

Hardware sends

You can also use hardware sends, available in the effect slots, to send a variable amount of the signal at that point in the signal chain to a hardware output. This is useful to integrate external effects, for example.

Internal busses

In AUM, internal busses has multiple functionality and covers subgroups, mixing, and effect sends.

To use a bus, you send audio into a bus by choosing it as output destination for a channel, or a corresponding bus send in an effect insert slot. Then receive the audio from the bus in one or more other channels, by choosing it as input source.

Main Mix

AUM doesn't have a built-in master or main mix. Instead, you're encouraged to use a bus for this.

For example, let all your channels output to Bus A, then add a channel which takes input from Bus A and outputs to hardware. This last channel now functions as a main mix channel, and gives you control of the master volume. It can also be used to apply insert effects like compression or EQ on the main mix.


In the same way, use several different busses for output, with corresponding bus channels, to have more than one mixes with individual master level controls and effects. The subgroup channels can in their turn output to a common main mix bus, etc.

Effect sends

In addition to using busses as output destinations, you can add one or more Bus Send in the effect slots. This will split the signal and send a variable amount of it to a bus. You can have several channels sending to the same bus, of course.

Add a channel that receives on the bus and then add effects such as reverb and delay on this channel. This effect-channel can output directly to hardware, or to yet another bus, etc. And it can contain other bus sends, that sends to other effect channels, and so on.

Drag the small knob next to the Bus Send node to control the amount of send.

Signal splitting

You can send to a bus, and then have several channels receiving on the same bus, thus splitting the signal so you can apply different effects in parallell, or route the same signal to several hardware outputs, etc.

Multi-bus Audio Unit plugins

AUM supports AU plugins with multiple inputs and/or outputs. This is useful for feeding side-chain signals into compressors, or getting separate outputs for drum parts, etc.

To access the extra busses of a plugin, tap an empty slot where you want the access point to be in your signal flow, and select "Multi-bus Audio Unit instances". This will list all currently loaded Audio Unit plugins that have extra busses.

After instantiating the plugin bus access node, tap the I/O graphics to the left of the node to select between the available inputs and outputs:

Input to Plugin Bus

Select which input bus of the plugin that should receive the signal entering this node. 'None' means the the signal is not sent to the plugin.

Plugin Bus to Output

Select which output bus of the plugin that should be sent out of this node. The first item is 'None' for source nodes (no output), and 'Pass-through' for effect nodes, which just passes the input signal through the node.

Inter-App Audio outputs

AUM has eight IAA output ports that can be loaded in other Inter-App Audio hosts.

Tap an empty output slot and choose "IAA / Audiobus Output", then select one of the ports. Load the corresponding port as an audio source in another host. It's not important in which order you do this. The port in AUM will show as disconnected until it's connected in another host.

A host transport panel will show up next to connected IAA output nodes, allowing you to control the transport of the connected host.


The IAA output ports mentioned above can also be used as Audiobus inputs.

AUM can also function as Audiobus output, receiving individual streams from connected inputs.

Simply connect AUM in the output slot in the Audiobus app, and AUM will automatically create channels for each connected input app. You can use the same input connection as source in several channels, for example to apply different effects in parallell.

Level metering

At the top center is the Level Meter. Tap it to choose the meter source. The meter can show the current levels of hardware inputs and outputs, internal busses, IAA / AB output ports, as well as the input or output levels of channels.

In addition, every channel has simple 3-dot peak meters on the input and output slots, for easy detection of optimal signal levels. Tap the dots to choose it as the Level Meter source. If the channel input/output is already the active meter source, then it will instead use the corresponding meter source for the node in that slot.

FilePlayer node

The built-in file player can play back previously recorded files, or any soundfile stored in AudioShare or any other location on your iOS device.

Controlling playback

The file player starts with the main transport clock, tap play in the upper left corner of the screen.

It only plays if the player is enabled, controlled by the circular toggle at the left side of the node. This toggle can be used also while the main transport is rolling, it will then start playing at the next sync quantum boundary (default 1 bar, can be set in the Clock Options) if SYNC is enabled for the player, or else it will start directly.

The play-enable toggle is also MIDI controllable. However, it's not suitable for rapid triggering, since the file player is disk based, not memory based.

Tap the node to show the File Player user interface. Here you can select the file, and setup looping and synchronization.


Load file

Tap the top row in the SELECTED FILE section to load a new file. This will allow you to browse any file stored in AudioShare. You can also tap the top right button in the navigation bar (looking like a folder with an arrow), to browse and select any file stored on your iOS device, including cloud services and external USB drives (iPadOS 13 required).


When enabled, the file will loop.


When enabled, the playback rate will be adjusted to keep it synchronized to current tempo, according to the original tempo of the file.

The playback rate may fluctuate due to small corrections made by Ableton Link. It's also adjusted when the amount of latency compensation changes, by speeding up or down for a short moment.

When disabled, playback rate is constant with no fluctuations, and the play-enable toggle will not wait for the next sync quantum before it starts.

Original BPM

The original tempo of the file, used for synchronization. If there is "nnn bpm" in the filename, it will be used as a default value.

Number of Beats

When both Loop and Sync are enabled, the tempo is instead derived from the number of beats in the file. The precise tempo will then be calculated according to this, to avoid drifting out of sync over time.

However, if you want to make it drift in a controlled way, you can double-tap the value and enter any decimal number. For example, a value of 4.5 would make it loop every 4 quarter-notes and 1 eight-note.


When Sync is OFF, you can control the playback rate of the FilePlayer freely using this parameter, which is also MIDI controllable.

Beat Offset

Introduces a negative or positive time shift for when the file starts playing. Can be used to offset loops for rhythmically interesting results, etc.


Normalizes the gain to -0.1 dB. Good for recordings with low levels, or to bring 32-bit files with clipping levels into range.

Built-in effect nodes

AUM has several built-in node types for signal processing, apart from the nodes for signal routing mentioned above.

Stereo Processing

Stereo Balance

Adjust the balance between the left and right channel.

Drag the small knob next to the node to control the balance.

Stereo to Mono

Convert stereo to mono by using only left, right or a variable blend between the two channels.

Drag the small knob next to the node to adjust the blend between left and right.

Stereo Panning

Similar to Balance, but instead pan left or right channels into the other channel.

Mid/Side Balance

Adjust the balance between mid and side. More side makes the stereo image wider.

By using this on two bus channels receiving on the same bus, with one on 100% mid and the other 100% side, you can apply different processing on mid and side, for example adding reverb to the side signal only.

Mid/Side-Stereo Convert

Convert the signal from M/S to L/R or the other way around.

Use this if recording with a real M/S microphone setup.

It can also be used for individual processing of Mid and Side signals with plugins that has individual controls for left and right, by putting this node before and after the effect(s).

This node also applies a gain of -3 dB, so that the net gain of two of these nodes equal 0 dB.

Invert Phase

Invert left, right or both channels.

Tap the toggles next to the node to select which channels to invert.

Filters and EQs

Parametric EQ

A single-band parametric equalizer.

Tap the node to adjust center frequency, Q, and gain.

The gain can also be controlled directly using the knob next to the node.

Low-shelf filter

A low-shelf filter to boost or cut low frequencies.

Tap the node to adjust cutoff frequency and gain.

The gain can also be controlled directly using the knob next to the node.

High-shelf filter

A high-shelf filter to boost or cut high frequencies.

Tap the node to adjust cutoff frequency and gain.

The gain can also be controlled directly using the knob next to the node.

Low-pass filter

A resonant low-pass filter to cut everything above a given frequency.

Tap the node to adjust cutoff frequency and resonance.

The frequency can also be controlled directly using the knob next to the node.

High-pass filter

A resonant high-pass filter to cut everything below a given frequency.

Tap the node to adjust cutoff frequency and resonance.

The frequency can also be controlled directly using the knob next to the node.

All-pass filter (1st order)

A first order all-pass filter, mainly useful for acoustic engineers and such.

All-pass filter (2nd order)

A second order all-pass filter, mainly useful for acoustic engineers and such.



A simple gain control.

Hard clip

Applies a gain control and then clips hard at +0dB.


Applies a gain control and then clips softly up to +0dB using a tanh curve.

Peak Limiter

Look-ahead peak limiter.

Tap the node to adjust attack time, decay time, and pre-gain.

The pre-gain can also be controlled directly using the knob next to the node.

This node introduces a latency equal to the attack time. Changing the attack time thus changes the latency compensation for the whole mix, which will produce some noises while being adjusted.

Plugin support

AUM can host Audio Unit Extensions (AUv3) as well as Inter-App Audio instruments, generators and effects.

Both kind of plugins receives host transport state and beat clock signal from AUM, for sample accurate synchronization (if implemented by the plugin).

A menu button will be shown to the left of the plugin node. Tap this to access MIDI routing for this node if it can receive MIDI. You can also double-tap the menu button as a shortcut for showing and assigning the built-in MIDI keyboard to this node only.

Instruments vs Generators vs MIDI processors

The difference between the types of plugins shown below the plugin names, is that Instruments and Music Effects can receive direct MIDI from the host (AUM in this case) without going through a separate Virtual MIDI port, while Generators and Effects does not have this ability.

MIDI processors are available only in the MIDI strips, and does not process audio signals but can receive and transmit MIDI.

Audio Unit Extensions

Audio Unit Extensions shows their user interface directly inside AUM in a floating window. Tap the node to show the plugins user interface.

Multiple instances can be created of the same Audio Unit Extension.

Double-tap the AUM background to close all open plugin windows.

Main parameter knob

AUM can expose a selected parameter of the Audio Unit plugin as a single knob or toggle next to the node. The selection is made in the MIDI Control view, which lists all the available parameters. (Note to devs: As a default, AUM will use the first parameter returned by parametersForOverviewWithCount.)

Instance name

When having multiple instances of the same plugin in the same channel strip, it's useful to set a name to identify them. You can do this by long-pressing the titlebar of the plugin window.

The name will be shown beneath the plugin icon in the node instead of the plugins "shortName" (if any), truncated to 6 characters. It will also be appended to the full plugin title as displayed in the title bar, MIDI connection lists and MIDI matrix.

You can also override the default node background color.

NOTE FOR DEVELOPERS: You can return a default value in audioUnitShortName for this. AUM parses some extra information in shortName. The format is `shortName:$rrggbb$` or `shortName;extraString;$rrggbb$` where rrggbb is in hexadecimal and sets the background color. ExtraString is displayed in the plugin title bar but not beneath the plugin icon.

You can emit a didChangeValueForKey on 'audioUnitShortName' to have AUM update this. Note that this would overwrite any custom instance name and color set by the user, so use carefully!

Multi-bus support

AUM supports Audio Unit plugins with multiple busses. See this section for more information.

Inter-App Audio

An Inter-App Audio (IAA) node run as a separate app. Tap the node to switch to the app.

To avoid "ghost IAA processes", make sure to always switch at least once to a hosted IAA app so that it becomes visible in the iOS multitask manager.

Latency compensation

AUM does latency compensation if an effect introduces a delay of the signal. The compensation is propagated through mix busses and sends, so that everything lines up at the end.

It also compensates for the total round-trip latency when recording hardware inputs. This can be disabled in the Settings.

Tap the DSP meter / battery indicator to show the current latency values and some other statistics, including the current time and date.

Inter-App Audio latency

Since IAA does not provide an interface to report latency, it can be adjusted manually in the node settings menu. Tap the menu symbol next to an IAA node and then the gear symbol.

However, some IAA nodes, like the AUFX audio effect series, does report latency to the host through a creative use of existing programming interfaces.

If you are a developer and would like to implement this in your own IAA app, take a look at this document. In short, the node sends the latency encoded as a Host Remote Event (latencyFrames<<8)|0xFF after connection to host, and when/if the latency changes.

Latency and synchronization

AUM uses Ableton Link for the transport clock, and compensates the current latency when calculating the current beat time.

This compensated beat time is used to sync IAA and AU plugins.

For IAA apps that syncs to Ableton Link, AUM compensates the timestamp used when processing these nodes, by adding any additional delay caused by latency compensation. It does not add the device hardware output latency, since Link apps are supposed to already do this.

Clock and transport

The transport controls are located at the top left of the screen.

The play button controls the transport clock, for starting and syncing file player nodes, hosted IAA apps and AU plugins.

The rec button controls recording in the app.

Drag left or right on the transport controls area to locate to another beat in the timeline.

Tap the tempo label to show the tempo menu, where you can adjust the tempo and access the Clock Options.

Tap tempo

You can tap out the tempo on the TAP button.


Tap the metronome symbol to enable or disable the metronome. The downbeat will be accentuated with a higher pitch, according to the current time signature.

Clock Options

Tap the three dots below the metronome button to show the Clock Options.

Time Signature

The number of beats per whole note. This value affects the metronome and the phase synchronization in Ableton Link.


The number of bars before time zero that the clock should start at. When recording, it will start recording at time zero, and this will function as a "count-in".

Sync Quantum

The number of bars for the synchronization interval used by the built-in FilePlayer, Recorder, and Ableton Link.

For example, a setting of 1 bar means that the beat time will be aligned on bar boundaries. The duration of a bar is decided by the current Time Signature.

While connected to an Ableton Link session, the transport will wait until the next sync quantum boundary before starting after pressing play.

Ableton Link

Tap to setup Ableton Link.

Ableton Link is a new technology that synchronizes beat, phase and tempo of Ableton Live and Link-enabled iOS apps over a wireless network. It lets you play devices together with the freedom of a live band. Anyone can start and stop their part while others keep playing, and anyone can adjust the tempo and the rest will follow. You can use Link to play with several instances of Ableton Live, with Live and iOS apps, or even without Live in your setup: using Link-enabled apps on multiple devices, or multiple apps on the same device.

Send MIDI Clock

Tap to enable or disable sending MIDI beat clock. To enable it, select a CoreMIDI destination for the clock.

This functionality allows you to synchronize external hardware such as sequencers. The clock is aligned to the audio output, compensating for device output latency. Trying to use this to synchronize other apps, or using it over wireless MIDI, will probably not align well!

When starting the transport from the beginning, or after locating to a specific beat, a MIDI START message is sent.

When pausing and starting again without rewinding or locating, a MIDI CONTINUE message is sent. The exception to this is when synchronized with Ableton Link, then it will wait for the next Link sync quantum (usually one bar) and then send a START message.

Metronome Level

Adjust the volume of the metronome.

Metronome Output

Tap to select the hardware output channel for the metronome.

Metronome Pre-Roll Only

When enabled, the metronome only sounds during the pre-roll phase.


Tap the circled R button on a channel to enable or disable recording for that channel. Then tap the red dot button in the transport controls at the top left of the screen to start recording.

If you tap record while the transport is rolling, it will start or end recording at the next sync quantum. This can be used to record loops on the fly.

Each recording-enabled channel will be recorded as a separate file. If you want to record a mix of several channels, use a mix bus!

Note that tapping the transport play button does not play back your recordings. The play button is just for controlling the transport clock. You can load the recording in a FilePlayer node if you wish to play it back as part of your mix.

Tap the menu button at the top right and choose "Files" to view your recordings. From there, tap a recording to play it back or export it in various ways.

The recordings are written directly into the file space of AudioShare, the audio file manager for iOS. You can use AudioShare to manage the recordings further, for example sharing them, doing some basic editing, normalizing and converting.

MIDI routing

AUM features a MIDI matrix that can connect MIDI from anywhere to anywhere, including externally connected MIDI devices, hosted nodes and plugins, and virtual MIDI endpoints.

Tap the Z-shaped curved symbol next to the main menu button to show the MIDI matrix.

The MIDI sources are listed at the top, and the destinations to the right. In the area between them is a grid of connection points. Tap a connection point to add or remove a connection.

If a MIDI source/destination is not available (For example MIDI controller unplugged, IAA app terminated, or AU plugin crashed), they will still be shown in the matrix if they are connected to anything else in the matrix. If the missing MIDI endpoint becomes available again, it will automatically re-connect in the matrix. If you remove all connections for the endpoint in the matrix, it will be hidden until the endpoint becomes available again.

Note that each individual app decides where it receives MIDI from, and where it sends MIDI to. If an app has Virtual MIDI ports, AUM can act as a MIDI router between that apps virtual ports and other MIDI endpoints.

Make sure you don't accidentally create double-connections, which would happen if you for example:

Also note that even though you have routed MIDI into an apps virtual port via AUM, it's no guarantee that the app will actually listen on its virtual port. Some apps need you to explicitly enable or select its virtual port as its MIDI source.

Plugin MIDI filtering

Hosted Inter-App Audio apps and Audio Unit Extension nodes that can receive direct MIDI from host gets their own MIDI destination in the matrix. These also include a MIDI filter to select specific channels and note ranges.

To show the filter settings, either tap the routing button in an AU plugin window title bar, or the IAA/AU node menu button, or tap the destination name in the MIDI routing matrix. This shows the list of connectable MIDI sources for this destination, and the MIDI filters at the bottom.

Select the channels that should be passed to this node by toggling each numbered channel button.

Adjust the note range by dragging the start and end note values.

In addition, you can choose to transpose the MIDI notes.

MIDI control

You can control the volume, mute, solo and rec toggles of all channels through MIDI. Additionally, each channel also allow control of any parameters of its nodes, including parameters of Audio Unit extensions. You can also control the global Transport, as well as loading saved sessions via MIDI commands.

Tap the menu button and choose "MIDI CTRL" to configure MIDI control. You can also reach the MIDI Controls for a specific channel by tapping the channel label and then the button that look like four sliders. In the same way, you can tap the similar button in an Audio Unit plugin titlebar to show all controls of that specific plugin instance.

It listens on the "MIDI Control" MIDI destination. Connect sources to this destination to use them for MIDI control, either by tapping the "MIDI Sources" shortcut at the top of the MIDI Control page, or by using the main MIDI routing matrix.

Mapping MIDI messages to controls

Tap a MIDI control parameter, and a panel will show up where you can configure the MIDI-channel, type and CC or note number that this parameter should respond to.

There are three kind of parameters: Values, Toggles and Actions.

Each parameter can listen to NOTE, CC, or PC (program change) messages. NOTE messages are mainly useful for Toggles and Actions.

For Value parameters, you can set the mapping range by tapping the "RANGE: 0 % -> 100 %" button and then adjust the min and max points.

For Toggle parameters, you can enable or disable TOGGLE mode. When enabled, the parameter is toggled on or off when receiving a non-zero value, useful for NOTE or momentary CC buttons. When disabled, the parameter is ON only while the NOTE is held, or when the CC value is above 64, useful for latching buttons. In this case you can also enable INVERT to reverse the on/off state.

Set the channel to 0 (OFF) to disable this parameter. You can also swipe left on the parameter in the list to reveal a "CLEAR" button.

Tap the LEARN button to initiate MIDI learn for this parameter, which will automatically configure the parameter to respond to the next incoming MIDI message.

Multiple parameters can be mapped to the same kind of MIDI message. When this is the case, a small warning triangle will appear. Tap it to see a list of all parameters mapped to this message.

Audio Unit Control Finder

Instead of scrolling through all the parameters of an AUv3 plugin, you can quickly show the MIDI control settings for a specific parameter.

To do this, activate the Control Finder by tapping the MIDI Control button (looks like four faders) in the plugin title bar, then tap the find-controls button (looks like a radiating knob) in the top right. You can also simply long-press the just mentioned MIDI Control button.

Once the Control Finder is activated for this plugin, tweak any parameter in the plugin and AUM will lookup and show the MIDI Control settings for it. If you tweak multiple parameters within a very short time window, all of them will be shown. (This is useful for XY-pad style controls, for example)

When the "Found Controls" popup is shown, configure the parameter as usual, and tap NEXT to find another one, or DONE to stop the Control Finder. You can also stop the Control Finder by tapping on the animated find-controls button in the plugin titlebar. Closing the plugin window will also stop it.

NOTE: MIDI Control is disabled while Control Finder is active, to avoid detecting parameters that are currently being externally modulated, etc.

Audio Unit Main Parameter selection

Audio Unit plugins can expose a single parameter as an easy-accessible knob next to the node.

To select which parameter should be exposed, tap on a parameter in the list and then toggle the knob-like symbol in the lower right corner so that it lights up in green color. Toggle it off if you don't wish to have a Main Parameter knob.

For developers: the default Main Parameter is choosen by calling parametersForOverviewWithCount:1 on the audio unit instance.

Audio Unit Preset Load actions

All Audio Unit plugins adds a built-in "Preset Load" sub-page for loading presets via MIDI actions. Tap the "ADD ACTION" button and select a preset to add an action for it. Then tap the action to configure which MIDI message it should trigger on. Swipe an action to delete it.

Audio Unit Show Plugin action

All Audio Unit plugins adds a built-in "Show plugin" action. Triggering this action will open the plugin window. Triggering again for the front-most plugin will close the window.

Transport Control

The "Receive MMC" toggle allows control of the transport clock with MIDI Machine Control. When enabled, AUM reacts to the MMC SysEx messages for play, stop and record.

There are also simple MIDI control items for rewind, toggle play and record, that can be controlled by MIDI note or CC messages, for example a connected MIDI pedal.

Session Load actions

The "Session Load" MIDI control sub-page allows you to add MIDI actions for loading specified sessions. Tap the "ADD ACTION" button and select a session to add an action for it. Then tap the action to configure which MIDI message it should trigger on. Swipe an action to delete it.


Tap the menu button and choose "Settings" to show the settings.

Audio Engine

Sample Rate

AUM always run in the current hardware sample rate, with no sample rate conversion.

The current sample rate is shown, tap it to select another preferred sample rate. On iOS, there's no guarantee that the preferred sample rate will be used, depending on device model, other running apps, and connected audio devices.

Buffer Size

Tap to select the preferred buffer size. As with sample rate, the current buffer size is not always under our control.

Larger buffer sizes means longer latency delay, but better stability with less risk for drop-outs.

Min. Latency

Set a minimum latency, taking into account any latency compensation already happening because of latency-introducing effect nodes.

This will reduce jitter for CoreMIDI destinations, since events can be timestamped in the future.

The latency will be compensated at the hardware audio outputs so everything aligns correctly.

Mic & Speaker

Input Gain

Adjust the hardware microphone gain.

High Quality

Enables measurement mode, which disables various iOS audio processing (filters and automatic gain control) for built-in input and output. This gives much lower latency, and can give higher fidelity and better bass response. You might need to increase the Mic Input gain and output level when enabled.


Bit Depth

This setting controls the bit depth of recorded audio. Choose between standard 16 and 24 bit signed integers, or 32 bit floating point.

32 bit floating point allows recordings with levels above +0dB without clipping, and the file can then be normalized or processed in other ways to bring it back to good levels.

Latency Comp.

When enabled, compensate for latency when recording hardware inputs, by shifting the recording in time according to the total round-trip delay of the audio system.

The compensation is only done on channels that has a hardware input as source, or a bus source that has hardware inputs feeding it (recursively).

Note that if you record hardware input mixed with other sources (FilePlayers, IAA/AU instruments, etc), also the non-hardware source will be shifted back and thus get out of sync on the recording. In those cases you might want to turn off latency compensation, or record the hardware inputs separately and mix it together with other sources as a later step.

Channel Defaults

Fader Level

The default level in dB for newly created channels. The default value is also set when double-tapping a channels volume fader.

First Effect Slot

Determines the pre/post fader position for the initial effect slot in newly created channels.

Send Amount

The initial send amount for newly created Bus Sends.


Auto-add Sources

When enabled, new Audiobus sources are automatically added as new channels.

Bluetooth MIDI


This brings up the standard Bluetooth LE MIDI Central view, where you can search for nearby devices and connect with them.

Once connected with a device, it will show up in the lists of available MIDI sources and/or destinations.


This brings up the standard Bluetooth LE MIDI Local Peripheral view, where you can advertise this device.

While this device is being advertised, another device can connect to it. Once connected, the other device will show up in the lists of available MIDI sources and/or destinations.

MIDI keyboard

AUM has a built-in keyboard to play notes. The keyboard is a MIDI source that can be routed to anything, including hosted nodes and plugins, other apps virtual MIDI ports, or connected external MIDI devices.

Tap the keyboard symbol in the lower left corner to show the keyboard.

Tap the wrench button to access the keyboard settings and select the MIDI destinations for the keyboard. The MIDI destinations can also be edited in the MIDI Routing section described above.

To quickly connect the keyboard to a single plugin (such as a synth), double-tap the menu button next to the node.


Main website:

Feel free to send me an email with any questions or problems!

Follow me on Twitter for news and other information.

If you like the app, please consider giving a review in the App Store, it really helps!

Privacy Policy

Find our privacy policy here: