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

1. Pick the player node:
   • AudioStreamPlayer — non-positional (music, UI, global SFX).
   • AudioStreamPlayer2D / AudioStreamPlayer3D — positional; volume/pan from distance.
2. Assign an AudioStream to stream (.ogg for music/loops, .wav for short SFX)
   and play(). Set autoplay for music that starts with the scene.
3. 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.
4. Control volume in dB, not linear (audio is logarithmic). 0 dB = unchanged,
   -80 dB ≈ silent. Convert with linear_to_db/db_to_linear.
5. Drive volume/mute from code with AudioServer by bus index.
6. 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.