godot-audio

SKILL.md

Godot Audio (4.x)

Play SFX and music, route them through buses, control volume in decibels, and time
gameplay to the beat. Targets Godot 4.7.

When to use

Use when playing sound effects or music, routing audio to buses (Master/Music/SFX),
adjusting volume/mute from code, adding bus effects (reverb, compressor), positional 3D
audio, or syncing events to music.

When not to use: engine-agnostic audio design (adaptive music structure, mixing
philosophy, ducking patterns) → audio-design; importing/encoding assets outside Godot.

Core workflow

Pick the player node:

AudioStreamPlayer — non-positional (music, UI, global SFX).

AudioStreamPlayer2D / AudioStreamPlayer3D — positional; volume/pan from distance.

Assign an AudioStream to stream (.ogg for music/loops, .wav for short SFX)
and play(). Set autoplay for music that starts with the scene.

Route to a bus. Set the player's bus to a named bus (e.g. "Music", "SFX").
Define buses in the Audio panel (bottom dock); each can have volume, mute, solo, and
effects.

Control volume in dB, not linear (audio is logarithmic). 0 dB = unchanged,
-80 dB ≈ silent. Convert with linear_to_db/db_to_linear.

Drive volume/mute from code with AudioServer by bus index.

For rhythm, compute precise playback time using output latency compensation.

Patterns

1. One-shot SFX (fire-and-forget)

@onready var sfx: AudioStreamPlayer = $Sfx   # stream assigned in the editor

func play_jump() -> void:
    sfx.pitch_scale = randf_range(0.95, 1.05)   # slight variation avoids fatigue
    sfx.play()

# For many overlapping copies, use an AudioStreamPlayer with an
# AudioStreamPolyphonic stream, or spawn short-lived players and free on `finished`.

2. Set a bus's volume and mute via AudioServer

func set_music_volume(linear_0_to_1: float) -> void:
    var bus := AudioServer.get_bus_index("Music")
    # Convert a 0..1 slider to decibels; clamp avoids -inf at 0.
    AudioServer.set_bus_volume_db(bus, linear_to_db(maxf(linear_0_to_1, 0.0001)))

func toggle_sfx(muted: bool) -> void:
    AudioServer.set_bus_mute(AudioServer.get_bus_index("SFX"), muted)

3. Crossfade between two music tracks

@onready var a: AudioStreamPlayer = $MusicA
@onready var b: AudioStreamPlayer = $MusicB

func crossfade_to(stream: AudioStream, secs := 1.5) -> void:
    b.stream = stream
    b.volume_db = -40.0
    b.play()
    var tw := create_tween().set_parallel(true)
    tw.tween_property(a, "volume_db", -40.0, secs)   # fade out current
    tw.tween_property(b, "volume_db", 0.0, secs)     # fade in next
    tw.chain().tween_callback(a.stop)
    var tmp := a; a = b; b = tmp                      # swap roles

4. Beat-accurate timing (compensate for output latency)

@onready var music: AudioStreamPlayer = $Music

func get_playback_time() -> float:
    # Add time since the last audio mix, subtract output latency, for sub-frame accuracy.
    var t := music.get_playback_position() + AudioServer.get_time_since_last_mix()
    return t - AudioServer.get_output_latency()

Pitfalls

Treating volume as linear. volume_db/set_bus_volume_db are decibels. Setting
volume_db = 0.5 is nearly full volume, not half. Map sliders with linear_to_db.

linear_to_db(0.0) is -inf. Clamp the linear value to a small minimum (e.g.
0.0001) before converting, or special-case 0 → mute.

Bus name typos fail quietly. get_bus_index("Muisc") returns -1; calls then error
or no-op. Match the exact bus name from the Audio panel.

Short SFX cut off when the same player is retriggered. Use separate players, an
AudioStreamPolyphonic, or AudioStreamPlayer per-shot freed on finished.

Music doesn't loop unless the import/stream loop is enabled (.ogg import has a
Loop option; AudioStreamWAV has loop_mode).

Syncing to get_playback_position() alone is jittery — it updates per audio mix,
not per frame; add get_time_since_last_mix() and subtract get_output_latency().

3D audio inaudible → no AudioListener3D/Camera3D to hear it, or max_distance/
attenuation too tight, or wrong bus muted.

References

For the bus layout (.tres), adding effects (reverb/compressor/EQ) and side-chain
ducking, AudioStreamPolyphonic/AudioStreamInteractive, microphone capture, and
procedural audio with AudioStreamGenerator, read references/buses-and-effects.md.

Related skills

audio-design — engine-agnostic adaptive music, mixing, and ducking practice.

godot-animation — syncing animation/Tween to get_playback_position().

godot-ui-control — volume sliders wired to AudioServer.