Mixer tracks

The Mixer is the strip section of the right-side Master Control panel. One MixerTrack per channel — gain / mute / solo / sends + its own FX chain — just like a DAW mixer. The key idea: a MixerTrack is an audio-side entity decoupled from the source that feeds it (the Ableton / Logic / Bitwig pattern). Sources (a Builder, a Faust .dsp) route INTO a track; the track owns the fader, the inserts, the sends, and routes on to master.

#Adding audio — the "+ ADD AUDIO" picker

Master Control starts with no tracks. You populate it explicitly:

• "+ ADD AUDIO" — lists the audio-shaped .builder DSPs in your project (Documents → PROJECT / assets/). Pick one; the IDE opens/mounts it as a Source and attaches its output to a MixerTrack. (FX-shaped DSPs — those with an Input node — appear under "+ ADD FX" instead and go to the Master-FX rack; see § 2.)

Attaching runs a 3-stage Auto-Create-mit-Reconnect resolver to decide which track the source lands on:

1. Persisted edge — if this source was attached to a track before, that routing is restored.
2. Name match — an existing track whose name equals the source's title.
3. Auto-create — otherwise a fresh track is created (named after the source) and the source routes into it.

#Anatomy of a track strip

Top-to-bottom:

• Label — the track name (defaults to the attached source's title; rename via mixer.tracks.rename).
• FX chain — per-track insert slots (see Per-track FX below). Distinct from the global Master-FX rack in § 2.
• Send sliders — one per Master-FX send slot, a level into that send bus (default 0).
• Mute / Solo — standard mixer semantics. Solo wins: when ANY track is soloed, only soloed tracks pass; un-soloed tracks are silenced regardless of their own mute. Multiple solos allowed.
• Gain fader — linear 0..1 (unity = 1.0), 5 ms ramp so live moves don't click. Display dB via 20 · log10(gain). Per-track L/R can be split (ganged: false) for balance.
• Per-track meter — post-gain peak of this track's contribution to master.
• × delete — removes the track (its inbound sources become unrouted, audio keeps running but silent until re-attached).

Track state (gain / muted / soloed / fxSlots / sendLevels / routesTo) persists in the project's mixerTracks slice of project.json, so your mix comes back on reload.

#Per-track FX

Each track has its own insert chain, independent of the global Master-FX rack. Append a Faust-DSP slot to a track via mixer.tracks.fx.add (compiled asynchronously — the slot appears immediately, wires in once compile succeeds), toggle bypass via enabled, set params via mixer.tracks.fx.set. Use per-track FX for channel-strip processing (EQ/comp on one source); use the Master-FX rack (§ 2) for bus-wide processing.

#Driving the mixer from MCP

Precondition for the chain: at least one MixerTrack exists (add one via "+ ADD AUDIO" or mixer.tracks.input.set — a fresh project has none, and the template below targets track 0).

actions:
  - action_id: surface.open
    input: { surface: faustwave-bundled/mixer }
    label: "▶ 0. Show Master Control (watch the faders move)"
  - action_id: system.state
    input: { sections: ["mixer_tracks"] }
    save_as: m
    label: "▶ 1. Inspect current tracks"
  - action_id: mixer.tracks.set
    input:
      track_id: "{{m.mixer_tracks.tracks.0.id}}"
      gain: 0.5
    label: "▶ 2. Drop the first track to −6 dB"
  - action_id: mixer.tracks.set
    input:
      track_id: "{{m.mixer_tracks.tracks.0.id}}"
      muted: true
    label: "▶ 3. Mute it"
  - action_id: mixer.tracks.clear
    input: { field: mutes }
    label: "■ Clear all mutes"

#The MCP actions

For AI & automation · MCP

A legacy mixer.set { module_id, … } + system.state { sections: ["mixer"] } slice still exist for per-Source-module Faust-param persistence (slotParams), but the visible faders are MixerTracks — reach for mixer.tracks.*.

#Sends — feeding a track into a Master-FX send slot

The Master-FX rack supports inserts (serial chain) and sends (parallel bus). Each track carries one send level per send slot — how much of THIS track to feed into that send bus:

1. master.fx.slots.list {}                          → slot ids (send slots included)
2. mixer.tracks.set {
     track_id: "<track id from system.state>",
     sends: { "<send slot id>": 0.4 }
   }

(Not a click-chain — the track id and send-slot id are yours to pick from step 1 and system.state { sections: ["mixer_tracks"] }.)

The sends map is set as a whole — omitting a slot removes its send. To keep a send wired but silent (for a smooth ramp-back-up), pass 0 for that slot id rather than omitting it.

#Common moves

• "Hear only one track, mute the rest" — mixer.tracks.set { track_id, soloed: true }. Solo wins.
• "Add my Hub snare to the mix" — install it (it lands in the project), then "+ ADD AUDIO" → pick it; a track auto-creates and the source routes in.
• "Disarm all solos and mutes" — mixer.tracks.clear { field: mutes } then { field: solos }.
• "Audition just one source" — set it soloed: true, listen, then mixer.tracks.clear { field: solos }.

Next section: the Master-FX rack — inserts vs sends, slot management, per-param control.