# Audio Buses

per-bus volume, mute/solo, and bus effects

```{raw} html
<a class="example-run-button" href="../demos/features_audio_buses.html">▶ Run in browser</a>


```

**Tags:** `audio` `buses` `effects` `mixing` `ui`

A synthesised arpeggio loop plays on the "Music" bus while periodic blips
fire on "SFX". Sliders set each bus's volume_db live, M/S check boxes drive
mute and solo (solo silences every bus off the soloed bus's routing path,
so a group bus keeps whatever is routed into it audible), and two
toggles put effects on the Music bus: a LowPassFilter whose cutoff sweeps
continuously, and a ReverbEffect switched on and off whole. Only the five
built-in buses (Master, Music, SFX, Voice, UI) are routable; a player's
`bus` property rejects any other name. Bus effects are silently inert on
the pure-Python fallback audio backend.


## What it demonstrates
- Routing players to buses via the `bus` property (set before play()).
- `AudioBusLayout.get_default()` and live `volume_db` / `mute` / `solo`.
- `effective_volume`: the dB chain walked through `send_to` up to Master.
- `send_to` as signal routing: a bus's output runs through its target's
  gain and effects, so an effect on Master processes every bus under it.
- Bus effects: `add_effect` / `remove_effect`, sweeping a biquad's
  `cutoff_hz` (clean), toggling a ReverbEffect whole (its parameters are
  never swept: changing them rebuilds the native chain audibly).

Controls:
  Sliders  - per-bus volume_db
  M / S    - mute / solo a bus (solo is ignored on Master)
  Toggles  - low-pass cutoff sweep and reverb on the Music bus
  B        - fire a blip on the SFX bus (or click the Blip button)
  ESC      - Quit

Run: uv run python examples/features/audio/buses.py
Headless self-check: uv run python examples/features/audio/buses.py --test

## Source

```{literalinclude} ../../examples/features/audio/buses.py
:language: python
:linenos:
```