Runtime Controls
Akkado patches can declare named UI controls that the web IDE turns into live inputs — sliders, momentary buttons, toggles, and dropdowns. Move them while the patch plays; hot-swap preserves their values across reloads, so you can tune a sound by ear without dropping audio.
Four builtins create controls:
| Builtin | Returns | UI widget |
|---|---|---|
param | signal (continuous) | Slider |
button | trigger (1 while held) | Momentary button |
toggle | signal (0 or 1) | On/off toggle |
dropdown | signal (0-based index) | Dropdown menu |
The controls are extracted at compile time. The IDE reads their metadata and renders the widgets next to the editor; values flow back through the runtime’s EnvMap, so every read returns the latest user-set value with no allocation.
param
Continuous parameter (slider) — exposes a named slider with a default, min, and max.
| Param | Type | Default | Description |
|---|---|---|---|
| name | string | — | Display label and lookup key |
| default | number | — | Initial value when the patch loads |
| min | number | 0 | Lower bound of the slider |
| max | number | 1 | Upper bound of the slider |
cutoff = param("cutoff", 800, 100, 5000)
osc("saw", 220)
|> lp(%, cutoff)
|> out(%)Names are display strings — spaces are fine (param("lfo rate", 0.4, 0.05, 6)). Each unique name produces one slider; calling param with the same name twice returns the same value.
button
Momentary trigger — outputs 1 while the user holds the button, 0 otherwise. Ideal for one-shot triggers.
| Param | Type | Default | Description |
|---|---|---|---|
| name | string | — | Display label and lookup key |
hit = button("Hit!")
sample(hit, 1.0, "bd") |> out(%)Press “Hit!” in the IDE to fire the kick sample on demand.
toggle
Boolean switch — outputs 0 or 1, click to flip. Use it as a gate or to switch between two signal paths.
| Param | Type | Default | Description |
|---|---|---|---|
| name | string | — | Display label and lookup key |
| default | number | 0 | Initial state (0 or 1) |
bypass = toggle("bypass", 0)
dry = osc("saw", 220)
wet = dry |> freeverb(%, 0.6, 0.5)
out(dry * bypass + wet * (1 - bypass))dropdown
Selection menu — outputs the 0-based index of the currently selected option. Up to five options after the name.
| Param | Type | Default | Description |
|---|---|---|---|
| name | string | — | Display label and lookup key |
| opt1 | string | — | First option (index 0) |
| opt2…5 | string | — | Additional options (indices 1–4) |
wave = dropdown("waveform", "sin", "saw", "sqr", "tri")
osc(wave, 220) |> out(%)Switching the dropdown returns 0, 1, 2, or 3; osc accepts the index directly.
Full example: live-tweakable bass-pad
This is the interactive-params.akk patch — a Moog-style bass with every knob exposed:
bpm = 100
cutoff = param("cutoff", 800, 100, 5000)
resonance = param("resonance", 2.0, 0.0, 4.0)
drive = param("drive", 1.5, 1.0, 6.0)
lfo_rate = param("lfo rate", 0.4, 0.05, 6.0)
lfo_depth = param("lfo depth", 0.6, 0.0, 1.0)
note_freq = param("freq", 110, 55, 440)
hit_trigger = button("Hit!")
hit = sample(hit_trigger, 1.0, "bd")
// Detuned saw stack for body
voices = saw(note_freq) + saw(note_freq * 1.005) + saw(note_freq * 0.997)
// LFO modulates the cutoff around the slider value
swept = cutoff + osc("sin", lfo_rate) * cutoff * lfo_depth * 0.6
voices * 0.2
|> moog(%, swept, resonance, _, drive)
|> @ + freeverb(@ + hit, 0.5, 0.5) * 0.35
|> out(%, %)Load it in the web IDE, hit play, and ride the sliders. Edit the code and re-evaluate — slider positions stay put, audio crossfades seamlessly.
How the IDE finds them
The compiler treats param / button / toggle / dropdown specially. Each call is rewritten to an ENV_GET opcode that looks the name up in the runtime’s EnvMap at audio-rate. At compile time, the call site’s name and (for param) min/max/default are exported to the IDE through akkado_get_builtins_json(). The IDE renders widgets from that metadata, and writes user input back into the same EnvMap — no extra registration step from the patch author.
Because lookups happen per-sample by name, you can declare the same control in multiple places without aliasing: every param("cutoff", …) reads the same slider.
Related
- Records as Builtin Options — the broader convention for richly-configured builtins.
- Hot-Swap — how the runtime preserves slider values when you re-evaluate code.