volume_duck

type: "volume_duck"

Scales one vanilla sound category down while the effect is active — a global duck, not a voice. There is no synthesis and no world position: every frame the effect sets its channel's game-options level to the pre-duck level times volume, blended by the fade weight, and hands the level back (restores the captured value) as soon as the duck ends.

Fields

Audio effects also accept the shared definition fields (duration, easing, loop, persistent, fade_ticks, sound). They do not accept screen_layer or order, and they render no geometry. volume_duck additionally ignores positions/region and entity anchors: it is global, not positional.

Field	Type	Default	Meaning
channel	float or string	0.0	Which sound category to scale: a name (master, music, records, weather, blocks, hostile, neutral, players, ambient, voice, ui, case-insensitive) or a SoundSource ordinal 0..10 (see the table below). Rounded when numeric, then clamped into range
volume	float	1.0	The target multiplier, 0..1, applied at full fade weight. 0.2 plays the channel at a fifth of its level

Both are ordinary animatable params: start/end, keyframes, expr, graphs, setParam and bind all work. volume's neutral is 1.0 (that is what the fade blends toward: no duck); channel has no neutral and is read as authored. The name form also works in datapack JSON ("channel": "music") and in commands (/vfx play vfxweaver:volume_duck {[channel:music],[volume:0.2]}); an unknown name warns once and the duck safely does nothing instead of ducking the wrong category.

The category level each frame is base × (1 - (1 - volume) × weight), where base is the level captured when the first duck touched that channel and weight is the effect's fade weight — so fade_ticks fades the duck in and out. Several ducks on one channel resolve last-writer-wins in active-list order.

channel	Category
0	Master
1	Music
2	Records (jukebox / music discs)
3	Weather
4	Blocks
5	Hostile creatures
6	Neutral creatures
7	Players
8	Ambient / environment
9	Voice / speech
10	UI

Example

{
    "type": "volume_duck",
    "duration": 100,
    "fade_ticks": 20,
    "params": {
        "channel": 1.0,
        "volume": 0.2
    }
}

Five seconds of music at a fifth of its level, fading in and out over one second each. Duck the hostile mobs instead for a stealth cue:

{
    "type": "volume_duck",
    "loop": true,
    "persistent": true,
    "fade_ticks": 40,
    "params": {
        "channel": 5.0,
        "volume": 0.0
    }
}

/vfx play vfxweaver:volume_duck

Honest limits

• Your sliders move under it. While a duck is active its channel's options-screen slider shows (and plays) the scaled level; a slider drag on that channel is overwritten the next frame, and the pre-duck level is restored when the duck ends — including a change you made mid-duck, which is lost. Channels no duck touches are never written.
• Nothing is saved. The scaled levels are applied through the live options and never written to options.txt; a restart always loads your saved levels.
• Recapture per activation. The pre-duck level is captured when the first duck touches a channel. Two ducks on different channels each capture and restore their own; two on the same channel share one capture, last-writer-wins.
• The ordinal table is vanilla's. A numeric channel indexes SoundSource.values() in game order; a future Minecraft reorder would shift the mapping (the names above are 26.1's). Prefer names ("channel": "music"): they resolve through the enum whatever its order. stopAll, world exit and client shutdown restore every ducked channel at once.