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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.

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 built with the same design system Mixel uses.

Where to go nextCopy Anchor Link

• Your first app: install mixel, make that app, and open it in Mixel. About five minutes.
• Build an app with your agent: Claude Code or Cursor, with the mixel MCP server, from an empty folder to a submitted app in about fifteen.
• Actions: controls, progress and Stop, results, and tests.
• Publish and review: what reviewers look at, and how updates reach people.

Not building an app? Your AI assistant connects Claude or Cursor to your own Library, and Ask your Library covers search in words.

Read a real appCopy Anchor Link

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: one action and the form Mixel draws. The place to start.
• Vocal Extractor, De-reverb and Pitch & Tempo: a model or a heavier job, with a page of their own.

How an app stays trustworthyCopy Anchor Link

• 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.
• 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.