Yusuf's Thoughts

MIDI Hardware Control

5 min read

Connect a physical MIDI controller - knobs, sliders, pads - to your TouchDesigner patch and control any visual parameter in real time. This is the foundation of a live VJ performance rig, turning a hardware controller into a fully custom control surface.

Operator Families in this Recipe

  • CHOPs (Channel Operators): Reading, filtering, and routing MIDI signal data.

Before You Start

You need a MIDI controller (e.g., Arturia MiniLab, Novation Launch Control, KORG nanoKONTROL). Connect it via USB. Most modern controllers are class-compliant and require no extra drivers - they appear instantly in TouchDesigner.

Part 1: Read the MIDI Signal

  1. Press Tab and add a MIDI In CHOP.
  2. Set the Device parameter to your controller’s name (the dropdown shows all connected MIDI devices).
  3. Set Active → On.
  4. Wiggle a knob or move a slider on your controller.

New channels will appear in the CHOP viewer. Each channel represents one physical control on your device.

Channel Naming Convention

  • Knobs and sliders (CC messages): Named ch1_ctrl[N] where N is the CC number. For example, ch1_ctrl7 = CC 7 on MIDI channel 1.
  • Pads and keys (Note messages): Named ch1_note[N] where N is the MIDI note number.
  • Pitch bend: Named ch1_pitch.

Move each control once to see exactly what channel it sends.

Part 2: Extract Specific Controls

  1. Add a Select CHOP after the MIDI In CHOP.
  2. In the Channel Names field, type the names of the channels you want, separated by spaces (e.g., ch1_ctrl1 ch1_ctrl7 ch1_ctrl10).
  3. Add a Rename CHOP after the Select CHOP.
    • In the From field (top line), list the original channel names.
    • In the To field (bottom line), list your new meaningful names: brightness, hue, speed.

Part 3: Remap to Useful Ranges

Raw MIDI values are integers from 0 to 127. Most visual parameters expect values in a 0 to 1 range.

  1. Add a Math CHOP after the Rename CHOP.
  2. Go to the Range tab:
    • From Range: 0 to 127.
    • To Range: 0 to 1 (for most parameters).
    • For hue offset: use 0 to 360. For rotation speed: use -1 to 1.
  3. Connect to a Null CHOP named CTRL.

Part 4: Bind to Visual Parameters

  1. Make CTRL active by clicking the + icon in its bottom-right corner.
  2. Navigate to the visual parameter you want to control (e.g., Brightness 1 on a Level TOP).
  3. Click and drag the channel from the CTRL viewer directly onto the parameter name.
  4. In the popup menu, select CHOP Reference for a live connection.

Part 5: Example VJ Setup

Build a minimal performance rig by mapping three controls:

ControllerChannelMapped to
Knob 1brightnessLevel TOP - Brightness
Knob 2hueHSV Adjust TOP - Hue Offset
Fader 1speedNoise TOP - Period (animation speed)

Now you can reshape the visuals live with your hands while the music plays.

Part 6: Using Pads as Scene Triggers

Pads send Note On (value = 64 or 127) and Note Off (value = 0) messages. To turn a pad press into a one-shot trigger:

  1. Add a Select CHOP and grab the pad’s channel (e.g., ch1_note36).
  2. Add a Trigger CHOP after it.
    • This converts the Note On/Off pair into a single clean pulse (0 to 1 and back).
  3. Feed the Trigger CHOP into a Count CHOP to cycle through visual scenes on each pad hit.

Troubleshooting

  • “No channels appear after wiggling controls.” - Check that Active is On on the MIDI In CHOP and try toggling it off and on again. Confirm the correct device is selected.
  • “Values jump erratically.” - Raw MIDI is integers; add a Lag CHOP (Lag In/Out: 0.04) between the Rename CHOP and the Null CHOP to smooth movement.
  • “Wrong channel prefix (ch2 instead of ch1).”** - Most controllers default to MIDI channel 1. Check your controller’s settings menu.
  • “Pad stays at 127 and never returns to 0.” - This is a Note On message. Use a Trigger CHOP to convert the on/off pair into a proper pulse.

Next Steps

  • Template it: Build this MIDI rig once, save as a .tox, and drop it into any future project for instant hardware control.
  • MIDI Clock sync: Use the MIDI In DAT with “MIDI Clock” mode to receive BPM timing pulses from an Ableton session and sync your visual tempo.
  • Two-way feedback: Use a MIDI Out CHOP to send values back to the controller (if it supports motorized faders or LED rings) for tactile visual feedback.

Parameter Tuning & Behavior

ParameterBehavior
Select CHOP FilterNarrow (specific names) = clean signal; Wildcard (ch1_ctrl*) = pass all CC from device.
Math Remap To RangeChange to match what the target parameter expects (e.g., -180 to 180 for rotation).
Lag SmoothingHigher = smooth, weighted knob feel; Lower = instant, snappy response to fast turns.
Trigger CHOPConverts note-on/off into a clean 0-to-1 pulse - ideal for scene switching and particle bursts.

Network Architecture

[ MIDI DEVICE ]
Controller ──────────────────────▶ MIDI In CHOP
                                         │
                                         ▼
                                  Select CHOP
                                  (ch1_ctrl1, ch1_ctrl7...)
                                         │
                                         ▼
                                  Rename CHOP
                                  (brightness, hue...)
                                         │
                                         ▼
                                  Math CHOP
                                  (0-127 → 0-1)
                                         │
                                         ▼
                                  Lag CHOP (optional smooth)
                                         │
                                         ▼
                              Null CHOP (CTRL) ──▶ CHOP Reference ──▶ Visual Parameters

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