---
title: "Music, Sound Effects, and Mixing"
description: "Route game audio through buses, scene music, spatial emitters, and mix snapshots."
canonical: https://docs.nodetool.ai/game-engine/audio
markdown: https://docs.nodetool.ai/game-engine/audio.md
product: NodeTool
source: https://github.com/nodetool-ai/nodetool/blob/main/docs/game-engine/audio.md
---

# Music, Sound Effects, and Mixing

Bind prepared audio to logical slots, then use scene music or entity audio sources to play it. Audio is presentation state. It does not change simulation results or deterministic replay.

![Audio routing diagram from scene music and entity effects through mixer buses to output](/assets/game-engine/audio-routing.svg)

*Scene music uses the music bus. Effects use sfx unless the asset-to-bus map selects another route.*

## Play a scene track or effect

![Kindle scene inspector showing music volume and fade tick settings](/assets/game-engine/editor-2d.png)

*Scene music settings beside the paused Kindle viewport. This capture shows configuration, not an audio playback test. [Capture provenance](/game-engine/screenshots).*

Set `scene.music` to an audio slot, volume, and optional fade-in and fade-out ticks. Music starts at scene entry. Pause suspends playback, reset starts the entry scene again, and restore resumes from the logical tick.

An entity's `audioSource.onEvent` responds to an event kind or emitted trigger name. Effects have separate voices so repeated triggers can overlap within the voice cap. Inspect the actual player after a gesture: browsers may block sound until the player clicks or presses a key. A silent image capture is not an audio playback test.

For a long music track, add `streaming` with loop start and optional loop end in seconds. The intro plays once, then the loop repeats. Browser media events determine custom streaming loop boundaries. Omit streaming for decoded playback.

## Route and balance

The mixer supplies master, music, sfx, voice, and ui buses. Custom buses have a parent, gain, mute state, low-pass frequency, and reverb send. A child multiplies its parent's gain. Muting sfx also mutes its descendants.

`assetBuses` routes a slot to a bus. Put dialogue on voice to use the default music ducking rule. The master limiter controls peaks. Replace ducking rules when the game needs a different relationship.

Mix snapshots override selected bus fields. Transitions enter a snapshot on a trigger, win, or scene entry and fade over ticks. The reserved base snapshot restores the ordinary mix. Restoring a session resets the appropriate mix without saving an audio graph in gameplay state.

## Place sound in space

Set `audioSource.spatial: true` for position-aware playback. The active camera is the listener. Minimum and maximum distance, distance model, and rolloff control attenuation. Doppler can shift pitch with relative motion.

3D sources can have a cone pointing along their −Z axis. 2D ignores the cone. The triggering event includes the emitter position so a collectible can disappear and still sound from where it was collected.

Check sounds on headphones and speakers, during pause and recovery, and after export. A configured audio asset may still fail to load or decode. Use the player's diagnostics and console to distinguish that from browser gesture restrictions.