UI: Global Controls (Pass 3)

This pass adds the four global controls — filter, delay, reverb, and master volume — as a panel sitting above the step grid. Two forms are needed: a reusable single-knob form (main_knob) and a grouping form (main_controls) that instantiates it four times.

The main_knob Form

Create the Form

Right-click patches -> main -> ui and choose Create new Form. Name it main_knob.

YAML

# form: "main_knob"

width: 60
height: 90
controls:
  cutoff:
    anchors: { hCenter: 0, top: 0, width: 60, height: 60 }
    type: knob
    props:
      parameterUid: "$parameterUid"
  cutoff.label:
    anchors: { bottom: 0, left: 0, right: 0, height: 30 }
    type: text
    props:
      text: "$title"

This form needs no Lua script. The knob’s parameterUid prop accepts the $parameterUid macro directly — the platform resolves the macro and wires the knob to the named parameter automatically. The parent form passes in a different UID for each instance and the correct parameter is connected without any additional code.

Press Apply after entering the YAML.

The main_controls Form

Create the Form

Create another new form and name it main_controls.

Assign Names and Copy the Required UID

Before entering the YAML, set up references for the three parameters needed: delay send level, reverb send level, and master volume.

Assign names to the send level knobs. In the main.flr layer editor, right-click the send level knob for the delay send, choose Assign name, and enter send_levels/delay. Repeat for the reverb send level knob, entering send_levels/reverb. These names can then be used directly in the YAML — no UID copy-paste needed.

Copy the master Amp’s volume UID. Right-click the Vol. knob on the master Amp processor and choose Copy Parameter UID. Keep this somewhere you can paste from — it goes into the YAML below. (This knob is left as a raw UID deliberately, to show that both approaches are always interchangeable.)

YAML

# form: "main_controls"

width: 460
height: 110
controls:
  bg.image:
    anchors: { left: 0, top: 0, right: 0, bottom: 0 }
    type: image
    props:
      image: main_controls_bg.svg

  cutoff:
    pos: { x: 15, y: 15, w: 60, h: 90 }
    type: subForm
    props:
      form: main_knob
      macroParameters:
        $title: FILTER
        $parameterUid: "externalCutoff"
  delay:
    pos: { x: 137, y: 15, w: 60, h: 90 }
    type: subForm
    props:
      form: main_knob
      macroParameters:
        $title: DELAY
        $parameterUid: "send_levels/delay"
  reverb:
    pos: { x: 259, y: 15, w: 60, h: 90 }
    type: subForm
    props:
      form: main_knob
      macroParameters:
        $title: REVERB
        $parameterUid: "send_levels/reverb"
  master:
    pos: { x: 381, y: 15, w: 60, h: 90 }
    type: subForm
    props:
      form: main_knob
      macroParameters:
        $title: MASTER
        $parameterUid: <copy+paste master Amp's volume knob UID>

Replace the <copy+paste … UID> placeholder for master with the UID you copied above.

The filter knob uses the global parameter name externalCutoff directly. The delay and reverb knobs use the names assigned just above. Only the master volume uses a raw UID — all three approaches resolve identically at runtime; the choice is purely about readability.

Press Apply after entering the YAML.

Wire into the Main Form

Open the main form’s YAML and add the master entry to the controls block:

width: 700
height: 560
controls:
  bg_image:
    anchors: { left: 0, top: 0, right: 0, bottom: 0 }
    type: image
    props:
      image: plugin_bg.png

  steps:
    pos: { x: 30, y: 63, w: 640, h: 72 }
    type: subForm
    props:
      form: step_grid

  stepControls:
    pos: { x: 30, y: 155, w: 640, h: 82 }
    type: subForm
    props:
      form: step_controls

  master:
    pos: { x: 120, y: 274, w: 460, h: 110 }
    type: subForm
    props:
      form: main_controls

  keyboard:
    pos: { x: 5, y: 423, w: 690, h: 130 }
    type: subForm
    props:
      form: keyboard

Press Apply. The global controls panel appears between the per-step controls and the keyboard.

The core instrument is now fully functional. The sequencer plays, each step’s parameters are independently editable, batch randomise works, and the four global controls shape the overall character of the sound.

Take a moment to play with what you have built: hold a key, let the pattern run, and use the global filter knob to sweep the sound. Try the per-step randomiser on different targets. Change notes on the keyboard mid-playback. This is a good point to get a feel for how the controls interact before moving on.

Expose the Filter to DAW Automation

With the instrument feeling good, there is one housekeeping step before moving on: registering externalCutoff as an automatable parameter so the DAW can record and replay filter sweeps.

Automatable parameters require a resolved UID — the parameter’s internal identifier — not just its name. Open Patch Settings → Global Parameters, find externalCutoff in the list, and right-click it to copy its UID.

Now switch to the Automatable Parameters tab in Patch Settings. Click + to add a new entry, paste in the UID you just copied, and set its display name to Filter — this is the label the DAW will show in its automation lanes.

The filter is now fully automation-ready. The DAW sees it as a named parameter, and because externalCutoff feeds through the RT script’s conversion function, any automation recorded against it will play back correctly regardless of whether the UI is open.

The only remaining piece is the spectrum visualizer, covered in the next chapter.