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MIDI

External MIDI devices can be integrated into Atrium’s mapping system, providing remote control over its parameters or tagalong buddies in clocked step.

Getting connected

Atrium has three hardware options for sending & receiving MIDI messages:

  • USB-A port: Connect an external controller via the USB-A port on the rear panel. Use your favorite knob box, MIDI keyboard, or sequencer! Up to 900mA of power is provided -- enough for most controllers.

  • USB-C port: Atrium will appear as a MIDI device (named "Atrium") on a connected computer. Exchange messages with your favourite DAW or other MIDI-enabled environment.

  • TRS-MIDI: Hardware MIDI devices can connect over TRS-MIDI via the midi in and midi out 3.5mm jacks (on the rear panel). midi in automatically accepts either type A or type B connections. midi out uses the more common type A pinout. If your device uses 5-pin DIN cables, you'll need adaptors.

When powering Atrium from a computer's USB port, the MIDI connection is available over this same cable. Otherwise, attach a cable to the computer port to communicate.

MIDI Input

Available are a few different classes of MIDI messages, as well as different workflows. Each set has it's own implications for use: note takeover dramatically changes the impact of Atrium's controls, while clock and CC input are a more natural fit into the map-centric workflow.

Notes

To treat Atrium as a more traditional "desktop synthesizer", you'll want to enable note control. This modal setting will take over note allocation, and sustain articulation.

Enter the MIDI input settings:

  • Press midi.

You'll see the interface go blank, apart from an X in the scale window & a dimly lit metronome.

Make sure to experiment with glide with MIDI, it's super fun.

  • Press scale to cycle through the voice allocation options:
  • X means no "takeover" is performed (this is the normal state).
  • P stands for "polyphonic", accepting MIDI messages to dynamically allocate pitches & articulate them with sustain.
  • U switches to "unison" mode, where all five voices are addressed by the most recent MIDI note.

Once you've selected your note allocation style, press midi to return to normal usage.

You'll notice a few things have changed:

  • notes and chord are disabled.
  • Playing notes on the keyboard will update the notes display.
  • sustain will be opened according to the velocity of your played notes.
  • scale will be blank, indicating "unquantized" mode.

But many things have not changed, and that's great! You can move around octaves, add glide to your notes, and even adjust voicing (in the downward direction) for some surprising voice spreading. Existing mappings to note and chord will still apply which can be quite confusing if you're not sure what's going on.

Map the tiniest amount of lfo to notes and spread out the voices with phase (sine is a great shape to start with). With polyphonic play you'll get that vintage warble, while unison becomes a massive drifting swarm. Add some glide and you'll be in bassline heaven.

While scale is disabled when entering a MIDI note mode, you can re-enable quantization by tapping scale. This can be helpful to stay in key, or provide a new interface into a "sequence" style scale.

Mapping Sources

Above the midi key you'll see three icons. From left-to-right these represent:

  • Mod Wheel
  • Pitch Bend
  • Aftertouch

When an attached MIDI device sends these messages, they are automatically exposed here, ready for mapping.

  • Hold map and press midi to select these MIDI sources.
  • Tap midi to cycle through the three options.
  • Each source can be applied as a mapping, just like a normal map source.
  • Press map to exit.

Map a little Pitch Bend to notes for traditional effects. The depth of the mapping affects the range of bend. The bend will be heard while mapping, so you can play the keyboard and notes slider simultaneously to find the right depth.

Try assigning your pitch wheel elsewhere!

CCs

Beyond these dedicated mapping sources, MIDI CC messages are also freely assignable. To achieve this, Atrium uses "MIDI learn" to create these assignments.

While this occurs outside the formal mapping system, the process is nearly identical, only differing in the method of source selection (ie. selecting a CC number):

  • Press learn to listen for MIDI CC messages. The cc light will pulse.
  • On your controller, move the knob/slider you will use to control Atrium. The cc light will illuminate solidly & this CC is selected as the source.
  • Move Atrium's controls to define the depth of modulation for this CC. The learned icon will light (three arrows pointing outward).
  • To assign a different CC, simply move the next knob/slider to be mapped.
  • As you send different CCs, the learned icon will indicate whether this CC has any existing mappings.
  • Press learn again to exit.

As you're learning CCs, any changes you make to the hardware controller will be immediately applied. This allows you to audition the full range of the mapping while configuring it. Use this feature to interactively find the right depth for your learnings.

Through MIDI learn, we're able to create types of macro controls that are otherwise not possible on Atrium itself. Consider learning a single CC to increase speed while decreasing tempo. Now your MIDI controller will increase the speed of some modulations, while decreasing others!

Clock

Atrium can receive MIDI clock via any input that's sending a clock signal. When enabled, the MIDI clock will override Atrium's internal clock:

  • Press midi to enter the MIDI input settings.
  • Press tap to toggle receiving MIDI clock. You'll see the metronome LED animation engage when enabled.
  • Press midi to exit.

Now Atrium's tempo knob acts as a clock multiplier/divider, with these divisions:

  • 1/4
  • 1/3
  • 1/2
  • 2/3
  • 1 (at noon)
  • 1.5
  • 2
  • 3
  • 4

MIDI clock input expects standard 24ppqn timing signals. Other timings will further multiply the range, though should remain musically relevant.

MIDI Clock Output

Atrium's MIDI output specification is still in its infancy. Presently only clock is supported, though this will change in future.

Clock

Share Atrium's clock via MIDI, through any (or all) of the ports:

  • Hold alt & press midi to select the MIDI output settings.
  • The extension window roughly displays an M for MIDI.
  • Press tap to enable clock output. The metronome will pulse.
  • Press alt to exit.

By default, Atrium will send its clock signal to all of the outgoing ports. To choose only a specific output destination:

  • Hold alt & press midi to select the MIDI output settings.
  • Press midi to cycle through the destination options.
  • Press alt to exit.

Each destination has an associated light, and by default they will all be on:

  • USB-A port: lights controller (piano keyboard icon).
  • USB-C port: lights computer (laptop icon).
  • TRS port: lights the midi key's window.