Capstone

Your library, at one volume. Drop in a folder of finished tracks and Capstone hands them back level with each other, with clipped peaks repaired and the tags still on them. Nothing leaves your machine, nothing touches the originals.

Half a DJ set is a volume fader. A 1994 CD rip sits ten decibels under last month's promo, and you find out about it in front of people. Capstone fixes that in a batch, offline, while you do something else.

What it does

• One loudness for everything. Every file lands on the same target, measured the way broadcast measures it, with a true-peak limiter so nothing distorts on the way there.
• Repairs clipped peaks. Finds the flattened transients a loud master or a bad rip left behind and puts a plausible curve back where the top was cut off.
• Fixes tracks that sit off pitch. Vinyl rips and tape transfers drift from concert pitch. Capstone measures how far and corrects it, keeping the tempo or moving it with the pitch, your choice.
• Optional warmth. A gentle or a tube saturation stage, driven at a fixed level so it does the same thing to a quiet rip as to a loud one.
• Multiband dynamics if you want them, four bands you can move.
• Templates. Save a set of settings, give it a name, use it on everything. Festival ships ready to use.
• Reads what you own, writes what you want. In: WAV, AIFF, FLAC, MP3, M4A, AAC, ALAC, CAF, OGG, Opus. Out: AIFF, WAV, FLAC, ALAC or MP3.
• Keeps your tags. Artist, title, album, genre and the rest ride through, so nothing comes back needing to be identified by ear.
• Never overwrites. Processed files are written somewhere new. Your originals are untouched.

Screenshots

The queue, mid-library. Cover art, clip count, dynamics, loudness and tuning per track.	The same thing in the light theme.

A template is the settings. The stock ones are read-only; duplicate one to change anything, and export it as a file if you want to hand it to someone.

Install

Grab the latest build from the releases page: a .dmg for macOS, an installer for Windows.

On macOS, if you see "Capstone is damaged and can't be opened", run this once:

xattr -rd com.apple.quarantine /Applications/Capstone.app

That warning appears because the app is not notarized with Apple yet. The command removes the quarantine flag macOS puts on downloaded files.

Using it

1. Drag files or a whole folder onto the Process Audio Files tab. Capstone starts measuring straight away, so you can see what is in there before you commit to anything.
2. Pick a template on Configure Template, or duplicate Festival and change it.
3. Choose where the output goes and in what format on Personalize.
4. Press Start Processing.

Build from source

You need Node.js 20+, npm, and Rust 1.87+. On macOS also the Xcode command line tools (xcode-select --install).

npm install
npm run tauri dev      # run it
npm run tauri build    # build an installer

Settings and templates are two JSON files in the standard app data directory:

• macOS: ~/Library/Application Support/app.capstone.desktop/
• Windows: %APPDATA%\app.capstone.desktop\
• Linux: ~/.local/share/app.capstone.desktop/

Open source

Capstone is MIT licensed — see LICENSE. Every dependency is permissive too, so you can read it, fork it, and ship your own build without asking anybody.

Issues and pull requests are welcome. If you are going to work on the audio engine, read the project context file in the repository root first: it explains why the processing stages run in the order they do, which is the part that is easy to get wrong.