# Start here

> Build small audio tools that run on a musician's own computer, and share them in Mixel's Apps section, where people review every app.

A Mixel app is a focused tool: split a song into stems, make a loop, convert a folder of takes. It runs on the person's computer, next to their Library, and it does one job well.

You write the work as a Python function. Mixel reads its parameters, draws the form, runs it in the background with progress and a Stop button, and puts what it makes into the Library.

```python title="app.py"
import numpy as np

import ox1audio as ox


@ox.action("Make it mono")
def mono(files: ox.Files("audio")):
    made = []
    for i, path in enumerate(files):
        ox.progress(i / len(files), path.name)
        samples, rate = ox.audio.read(path)
        folded = np.mean(samples, axis=1, keepdims=True)
        out = ox.audio.write(folded, rate, "wav", name=f"{path.stem} mono")
        made.append(ox.sound(out, title=f"{path.stem} mono"))
    return made
```

That's the whole app, apart from `app.json`, which says its name and what it may touch, and `pyproject.toml`, which lists numpy. `mixel new` writes both. When the drawn form isn't enough, add a [page](https://docs.0x1audio.com/page.md) built with the same design system Mixel uses.

## Where to go next

- [Your first app](https://docs.0x1audio.com/start.md): install `mixel`, make that app, and open it in Mixel. About five minutes.
- [Build an app with your agent](https://docs.0x1audio.com/tutorial.md): Claude Code or Cursor, with the `mixel` MCP server, from an empty folder to a submitted app in about fifteen.
- [Actions](https://docs.0x1audio.com/actions.md): controls, progress and Stop, results, and tests.
- [Publish and review](https://docs.0x1audio.com/publish.md): what reviewers look at, and how updates reach people.

Not building an app? [Your AI assistant](https://docs.0x1audio.com/assistant.md) connects Claude or Cursor to your own Library, and [Ask your Library](https://docs.0x1audio.com/ask.md) covers search in words.

## Read a real app

The apps 0x1audio makes for Mixel are open source under the Apache 2.0 licence, and they're built with the same `mixel` and SDK as yours:

- [Audio Converter](https://github.com/0x1audio/0x1audio-converter-app): one action and the form Mixel draws. The place to start.
- [Vocal Extractor](https://github.com/0x1audio/0x1audio-uvr-app), [De-reverb](https://github.com/0x1audio/0x1audio-sonic-dryer-app) and [Pitch & Tempo](https://github.com/0x1audio/0x1audio-audiowizard-app): a model or a heavier job, with a [page](https://docs.0x1audio.com/page.md) of their own.

## How an app stays trustworthy

- **It asks first.** An app lists what it needs in `app.json`, each with one sentence that says why. The person reads those before it opens, and anything else is refused. See [Permissions](https://docs.0x1audio.com/permissions.md).
- **It's reviewed.** People review every version before it reaches Mixel's Apps section, and installs are pinned to the exact code they reviewed.
- **It's checked before review.** `mixel check` applies the same rules the reviewers do, and every error ends with the line that fixes it.

**For coding agents.**
Start with [AGENTS.md](https://docs.0x1audio.com/agents.md): the whole contract in under 2k tokens. Every page here has a markdown twin at its URL plus `.md`, and [/llms.txt](/llms.txt) lists them all.