AudioTune

Per-app volume control for macOS — a quick mixer in the menu bar, plus a full window when you want more room. No kernel extension, no audio driver: it uses the modern Core Audio process-tap API (macOS 14.4+) to tap each app's audio, mute its direct output, and re-render it through a private aggregate device at an adjustable per-app gain.

Features

• Per-app volume sliders, live as you drag — from the menu bar or the window
• Per-app mute
• Master channel — one slider/mute scaling every app
• Pin apps to keep them in the main menu (vs. the "All apps" submenu)
• Stays out of the way — lives in the menu bar only; a Dock icon appears just while the window is open
• Persistent — levels are remembered per app (by bundle id) across launches
• Auto-attach — a saved level re-applies the moment an app starts playing
• Follows your output device — rebuilds taps when you switch headphones/speakers
• Presets — save your mix as "Work", "Gaming", "Streaming" and switch in one click from the window, the menu bar, the Dock menu, or a shortcut
• Per-device presets — bind a preset to an output device and it applies itself the moment that device becomes the default. Plug in your earbuds and your earbud mix loads automatically; devices you haven't bound behave exactly as before.
• Global keyboard shortcuts — control audio from anywhere, fully rebindable:
  • ⌃⌥↑ / ⌃⌥↓ — raise / lower the focused app's volume (5% steps, repeats while held)
  • ⌃⌥M — mute / unmute the focused app
  • Bind your own for the master channel, for specific apps, and for presets
  • A small on-screen HUD shows the change (like the system volume overlay)
• Light / Dark / System appearance — System follows the OS and updates live
• Launch at Login toggle

Using it

AudioTune runs in the menu bar. Click its icon for the quick mixer: the master slider, every app that's playing, and a Preset submenu.

For the full interface choose Open Window (⌘O) from that menu. The window has three tabs:

Tab	What's there
Mixer	Master plus every app, with slider, mute and pin
Presets	Save the current mix as a named preset; apply, rename, update or delete it, give it a shortcut, or bind it to an output device so it loads automatically
Shortcuts	Rebind the global shortcuts and assign raise/lower/mute shortcuts per app

A shared footer — Reset all, appearance, Launch at Login — sits under all three tabs. Closing the window leaves AudioTune running in the menu bar.

Requirements

• macOS 14.4 or later (Apple Silicon or Intel)

Install

Option A — download the prebuilt app

1. Grab AudioTune.zip from the latest release and unzip it.
2. Move AudioTune.app to /Applications.
3. First launch only: because the app isn't notarized, macOS blocks it once. Either:
   • Open it, then go to System Settings → Privacy & Security, scroll down, and click "Open Anyway", or
   • run this in Terminal to clear the download flag:

     xattr -dr com.apple.quarantine /Applications/AudioTune.app

4. The first time you move a volume slider, macOS asks for audio-recording permission — click Allow (this is what lets AudioTune tap app audio).

Why the warning? AudioTune is open-source and ad-hoc signed, not notarized through Apple's paid program. The warning is about distribution, not safety — the code is all in this repo. It works identically once past the first launch.

Option B — build from source (no Gatekeeper prompt)

Needs the Swift toolchain (Xcode or Command Line Tools). Locally-built apps aren't quarantined, so there's no warning:

git clone https://github.com/ZechariahJ/audiotune.git
cd audiotune
./build.sh            # -> AudioTune.app (ad-hoc signed, local use)
open AudioTune.app

Permissions

AudioTune needs audio-recording permission to tap other apps' audio. The first time you move a volume slider, macOS shows the prompt — click Allow.

This is a one-time grant, not per-launch. macOS remembers it across every future open, and you can review or revoke it under System Settings → Privacy & Security → Microphone (audio capture is grouped under "Microphone").

You may be asked to approve again if you install a new version (a different build has a different signature) or build from source repeatedly — each build looks slightly "new" to macOS. Normal day-to-day use never re-prompts.

Layout

Audio engine

File	Role
ProcessTap.swift	Tap + aggregate device + realtime gain render callback
AudioProcessMonitor.swift	Enumerates Core Audio process objects → app roster
CoreAudioHW.swift	Default output device helpers
AudioMixer.swift	Shared state: app roster, levels, presets, hotkey dispatch

Interface

File	Role
main.swift	Entry point; starts as a menu-bar-only (accessory) app
AppDelegate.swift	Menus, window lifecycle, hotkey registration, device listener
MainWindowView.swift	Window tabs: Mixer / Presets / Shortcuts
MixerView.swift	Mixer tab
ProfilesView.swift	Create, apply, rename and delete presets
ShortcutsView.swift	Rebind global and per-app shortcuts
WindowFooter.swift	Shared footer: reset, appearance, launch at login
AppVolumeRowView.swift	A menu row: icon, name, slider, mute, pin
KeyRecorder.swift	Click-to-record shortcut field
VolumeHUD.swift	On-screen overlay shown when a shortcut changes volume

Supporting

File	Role
GlobalHotKeys.swift	System-wide hotkeys (Carbon), with hold-to-repeat
Profiles.swift	Preset + hotkey models
SettingsStore.swift	Persisted levels, presets and shortcuts (UserDefaults)
LoginItem.swift	Launch-at-login via SMAppService
Log.swift	Size-capped diagnostic log in ~/Library/Logs/AudioTune

Privacy

AudioTune makes no network requests — no telemetry, no analytics, no auto-update — and asks for exactly one permission (audio recording, required by the tap API). Tapped audio is never written to disk. See SECURITY.md for details and how to report a vulnerability.