sound-effect

/sound-effect — Generate a Short SFX One-Shot and Wire It

Overview

This skill produces one named SFX clip aligned with the audio bible's vocabulary, then wires it into the scene as an AudioStreamPlayer that plays once and frees its parent (or stops cleanly if it's a looped texture). The shape of the prompt is what makes the difference between "metal sword swing whoosh, dry, sharp, 250ms" returning the right clip on the first try and "epic battle sound" returning twenty seconds of musical noise.

ElevenLabs SFX (the sound_effects capability of summer_generate_audio) is literal. It treats the prompt as a description of a real sound, not as a vibe. Concrete material + action + intensity beats adjectives every time.

When to use

• One-shot SFX: footstep, swing, click, hit, impact, pickup, jump, land, door, breath.
• Short loops < 2s: hum, drone snippet, rain texture (for very short looping ambients prefer audio/ambient-bed).
• Replacing a placeholder beep with something on-bible.

When NOT to use

• Music or musical stings → audio/music-track.
• Long location ambience (>5s) → audio/ambient-bed.
• Voice / dialogue → audio/voice-line.
• Defining the vocabulary of SFX — that's audio/audio-direction. This skill executes against an existing bible.

Steps

1. Read the audio bible

Read .summer/audio-bible.md

If it doesn't exist, ask:

No audio bible at .summer/audio-bible.md. Want to run /audio-direction first to define the SFX vocabulary, or shall I just one-shot this with sensible defaults?

The bible defines an SFX class (UI, Pickup positive, Damage, Footstep, Attack, Stinger, Ambient layer, Pickup neutral). Map the user's request to a class. Quote the class's character and DON'Ts back so the prompt obeys them.

2. Search for an existing clip first

Generation is metered. Reuse beats regenerate.

summer_search_assets(query="<class> <subject>", filter={ kind: "audio" })

If something fits, ask:

Found audio/sfx/sword_swing_01.wav. Use this, or generate fresh?

3. Build the prompt — subject + material + action + intensity + duration cue

ElevenLabs SFX responds to literal sound descriptions. Pattern:

<subject> <material> <action>, <intensity>, <character>, <duration cue>

Working examples (these produce the right clip on the first try):

Goal	Prompt that works	Why
Sword swing	metal sword swing whoosh, dry, sharp, 250ms	material + action + dry rules out reverb
UI click	soft woody UI click, short, neutral pitch, 80ms	material + duration; "click" alone is too vague
Footstep on stone	single footstep on dry stone, leather sole, mid-weight, 180ms	surface + footwear + body weight
Player hit	punchy low-mid body hit impact, slight detune, no tail, 200ms	"no tail" kills reverb the bible forbids
Coin pickup	bright metallic coin pickup, warm major-third interval, 300ms, light room reverb	named interval = melodic shape
Door creak open	old wooden door creak opening slowly, 1.2s, dry interior	duration + space
Bow draw	recurve bow draw, taut string, leather grip, 600ms	material specificity
Magic cast	short ice magic cast, crystalline shimmer, ascending, 500ms	element + pitch motion

Prompts that DON'T work (and why):

Bad prompt	Failure mode
epic sword sound	"Epic" is a vibe; the model can't render a vibe. Returns generic noise.
cool UI click	No material, no duration. Returns a 5-second synth blip.
the sound when the player gets hit really hard and falls down	Multiple events. Model tries to render all and returns nothing coherent. Split into two SFX.
swoosh	Underspecified. Returns inconsistent character every regen.
realistic gunshot	"Realistic" is a constraint, not a description. Use 9mm pistol shot, indoor, sharp crack, short tail, 400ms.

4. Confirm and call

Show the prompt and the call before running:

Prompt: metal sword swing whoosh, dry, sharp, 250ms. Duration 0.5s (model floor). Model: ElevenLabs SFX. Cost: ~1 credit. Generate?

summer_generate_audio(
  capability: "sound_effects",
  prompt: "metal sword swing whoosh, dry, sharp, 250ms",
  durationSeconds: 0.5
)
// Result: { asset: { fileUrl, ... } }
// Then: summer_import_from_url(url: "<fileUrl>", path: "res://audio/sfx/sword_swing_01.wav")

durationSeconds floor is 0.5, ceiling is 22. If the user wants a 100ms click, generate 0.5s and the player only plays the front; or trim in the engine.

5. Decision: one-shot vs loop

Use case	Setup
Footstep, swing, click, hit	One-shot AudioStreamPlayer, autoplay=false, fired by code or animation.
Short hum / drone < 2s	Set the imported AudioStream loop=true in the import dock.

For one-shots, set Loop OFF on the import. Default ElevenLabs returns are not loop-clean — looping a one-shot will click.

6. Wire it into the scene

Choose the right player node:

Node	Use for
AudioStreamPlayer	UI, music, non-positional (HUD click, menu confirm)
AudioStreamPlayer2D	2D positional (top-down hit, 2D pickup)
AudioStreamPlayer3D	3D positional (footstep on a 3D character, weapon swing in world)

Add it under the emitting node:

summer_add_node(parentPath="/root/Game/Player", type="AudioStreamPlayer3D", name="SwingSFX")
summer_set_prop(path="/root/Game/Player/SwingSFX", property="stream", value="res://audio/sfx/sword_swing_01.wav")
summer_set_prop(path="/root/Game/Player/SwingSFX", property="bus", value="SFX")
summer_set_prop(path="/root/Game/Player/SwingSFX", property="volume_db", value=0.0)
summer_set_prop(path="/root/Game/Player/SwingSFX", property="max_distance", value=25.0)
summer_set_prop(path="/root/Game/Player/SwingSFX", property="attenuation_model", value=0)

Bus name must match the bible (SFX, UI, Ambient, etc.). If the bus doesn't exist, run /audio-direction step 8.

7. Spawn-and-free pattern (one-shots in flight)

For SFX that needs to outlive the emitter (player dies but the death-blow SFX should finish), instantiate a small scene with this script:

# scripts/audio/SfxOneShot.gd
extends AudioStreamPlayer3D

func _ready() -> void:
	finished.connect(queue_free)
	play()

Save it as a .tscn, then summer_instantiate_scene at the emitter's global position when the event fires. The node frees itself when the stream finishes — no leaks.

8. Volume calibration

If the clip comes back too quiet:

• First try volume_db on the player (+3 to +9 typical).
• If still quiet, the clip itself is hot-low — regenerate with a louder intensity word: loud, forceful, heavy.
• Never push volume_db past +12; clipping artifacts.

If it comes back too loud (rare): negative volume_db, or trim attack in an editor.

9. Confirm in scene

summer_inspect_node(path="/root/Game/Player/SwingSFX")

Verify stream, bus, volume_db. Trigger it via summer_play if the user wants to hear it now.

Reference card — prompt patterns by class

UI click:        soft woody UI click, neutral pitch, 80ms
UI confirm:      affirmative UI chime, warm minor-third, 250ms
UI error:        flat UI buzz, slight dissonance, 200ms
Pickup positive: bright pickup, ascending major-third, 300ms, light reverb
Pickup neutral:  small tactile pickup, no melody, 150ms
Footstep wood:   single footstep on hollow wood floor, leather sole, 180ms
Footstep grass:  single footstep on damp grass, soft, 200ms
Footstep stone:  single footstep on dry stone, mid-weight, 180ms
Hit body:        punchy body hit, low-mid thump, no tail, 200ms
Hit metal:       metal-on-metal clang, sharp transient, short ring, 350ms
Swing whoosh:    fast air whoosh from a swung blade, dry, 250ms
Door creak:      old wooden door creak opening, 1.2s, dry interior
Magic ice:       crystalline ice cast, ascending shimmer, 500ms
Magic fire:      whoosh of fire ignition, low rumble, 700ms
Stinger event:   short triumphant brass stinger, 1.5s, hall reverb

Anti-patterns

• Adjective-only prompts. epic, cool, realistic, professional — meaningless to the model.
• Multiple events in one prompt. Split into two generations.
• Looping a non-loop-clean clip. Will click. Use audio/ambient-bed for actual loops.
• Skipping the bus. Default bus is Master. SFX must route to the SFX bus or the mix breaks.
• Generating before searching. Reuse before regenerate.
• Generating before reading the bible. The clip will fight the rest of the audio.

Edge cases

• Clip too quiet: volume_db first; regenerate with louder intensity word second.
• Clip too long: trim in audio editor or set AudioStreamPlayer to stop() on a timer.
• Footstep needs surface variants: generate one per material (wood / stone / grass / metal / dirt) and switch in code based on raycast on the floor's physics_material.
• SFX for an animation event: wire to the animation's Call Method Track, not to _process.

Fallback (no MCP)

Print the call:

ElevenLabs SFX prompt: "metal sword swing whoosh, dry, sharp, 250ms"
Duration: 0.5s
Save to: audio/sfx/sword_swing_01.wav

Tell the user to run it via the Summer dashboard, then summer_import_from_url the result.

Handoff

After the SFX is wired:

SFX sword_swing_01.wav wired to Player/SwingSFX on the SFX bus. Next:

• Trigger it from your attack animation's Call Method Track → play().
• Generate the parry / clash counterpart with /sound-effect again.
• For a full footstep system across surfaces, see audio/footstep-systems.

See also

• audio/audio-direction — defines the vocabulary this skill obeys
• audio/ambient-bed — long looping textures
• audio/music-track — music
• audio/voice-line — TTS
• references/mcp-tools-reference.md
• references/godot-version.md — Godot 4.5 audio nodes