---
title: Utility
description: "A utility as a device you can plug in: a gain, a pan, a width, mono and a phase invert as a state, a panel, a Web Audio engine and the tools an agent drives it with."
component: true
base: base
---

<ComponentPreview styleName="base-nova" name="block-utility" />

Sets the level and the stereo image: a gain, a pan, a width from mono to twice as wide, a mono switch and a phase invert. It has no display, so its panel is only as tall as its knobs. It is a device like the [compressor](/docs/components/compressor): a state, a panel that draws it, an engine that plays it and tools an agent calls, each its own file.

## Installation

<CodeTabs>

<TabsList>
  <TabsTrigger value="cli">CLI</TabsTrigger>
  <TabsTrigger value="manual">Manual</TabsTrigger>
</TabsList>

<TabsContent value="cli">

```bash component
npx shadcn@latest add @audio-ui/block-utility
```

</TabsContent>

<TabsContent value="manual">

<Steps>

<Step>Install the packages:</Step>

```bash
npm install @audio-ui/react @audio-ui/core
```

<Step>Add the pieces you want. All of them, or only the state and the panel if your engine is elsewhere:</Step>

```bash
npx shadcn@latest add @audio-ui/utility-device @audio-ui/utility-panel @audio-ui/utility-engine
```

<Step>Copy and paste the demo that wires them, if you want it.</Step>

<ComponentSource
  styleName="base-nova"
  name="block-utility"
  title="components/examples/block-utility.tsx"
/>

</Steps>

</TabsContent>

</CodeTabs>

## Usage

```tsx
import { UtilityPanel } from "@/components/audio-ui/devices/utility/panel";
import { utilityDevice } from "@/components/audio-ui/devices/utility/device";

const [state, setState] = useState(() => utilityDevice.defaults());

<UtilityPanel onValueChange={setState} value={state} />;
```

The state is a plain object keyed by parameter id, so a host stores it, saves it with its project and sends it where it likes. `utilitySettings(state)` gives the numbers that go on the nodes.

## The engine

```ts
import { createUtilityEngine } from "@/components/audio-ui/devices/utility/engine";

const engine = createUtilityEngine(ctx, state);
source.connect(engine.input);
engine.output.connect(ctx.destination);
engine.update(nextState); // parameters ramp: no click
engine.dispose();
```

The signal is split into mid and side. The width scales the side: 0 is mono, 100 % is the input as it is, 200 % is twice as wide. A mono input is spread to both sides first. Off, the signal passes unchanged.

## The tools

```ts
import { deviceTools } from "@audio-ui/core/device";
import { utilityDevice } from "@/components/audio-ui/devices/utility/device";

const [set, reset] = deviceTools(utilityDevice);
```

`set` and `reset` change the state, with the ranges the device enforces: a value out of range is brought in and reported, a wrong one is refused by name, and a call never throws.

## Accessibility

Every control is a native input: the knobs are sliders named after their parameter, with the value and unit as the text value, the switches are toggle buttons, and everything takes the keyboard.