Anatomy of a DSP — and your first one — Faust DSP (.dsp)

A minimal generator DSP is three lines:

import("stdfaust.lib");
level = hslider("level", 0.3, 0, 1, 0.001);
process = os.osc(440) * level;

import("stdfaust.lib") mounts the standard library under its usual two-letter prefixes (os. oscillators, fi. filters, en. envelopes, no. noise, ba. basics, ma. math, …).
Every hslider / nentry / button / checkbox becomes a live knob in the module's UI panel and a param path the AI can read and write.
process is the DSP's signal function. Generator shape means no audio inputs: process = <expression>;. Mono output is fine — split to stereo with <: _, _ when you want both channels.

Two shapes the editor treats differently:

Shape	Example	Where it runs
Generator	`process = os.osc(f);`	A `.dsp` module (this book)
FX	`process = _ : fi.lowpass(1, fc);`	Master-FX or track-FX slots — a standalone `.dsp` module has no input source, so Run refuses it with a friendly error. Validate FX sources with `dsp.compile` instead.

Build one hands-free

actions:
  - action_id: documents.add
    input: { type: "faust-dsp", title: "Tutorial Tone" }
    save_as: mod
    label: "▶ 1. Create a .dsp module (file lands in assets/)"
  - action_id: editor.source.set
    input: { module_id: "{{mod.module_id}}", source: "import(\"stdfaust.lib\"); level = hslider(\"level\", 0.2, 0, 1, 0.001); process = os.osc(440) * level <: _, _;" }
    label: "▶ 2. Write a sine-tone source into the buffer"
  - action_id: dsp.run
    input: { module_id: "{{mod.module_id}}" }
    label: "▶ 3. Compile + start the worklet"
  - action_id: mixer.tracks.input.set
    input: { module_id: "{{mod.module_id}}", source_title: "Tutorial Tone" }
    label: "▶ 4. Attach to a mixer track — now it is audible"
  - action_id: dsp.stop
    input: { module_id: "{{mod.module_id}}" }
    label: "▶ 5. Stop the tone (strip + file survive)"

#Build one hands-free

Build one hands-free