What is soundknobs?

SoundKnobs is a small macOS menu-bar app that gives you a separate volume slider for each app currently playing audio on your computer. If you have music playing in Spotify, a video in Safari, and a call in Zoom at the same time, each one gets its own row in the menu with a slider and a mute button. Adjusting any one of them changes only that app's volume, leaving the others untouched. The app does not install any background system extensions or kernel drivers. It uses a public macOS audio feature called a process tap, which lets it intercept an app's audio stream, scale the volume to whatever level you set, and send the result to your speakers or headphones. Quitting SoundKnobs immediately restores normal audio behavior for every app. The one permission it requests is System Audio Recording, which macOS requires for this kind of tap even though nothing is ever recorded or saved. Installing it requires no building or developer tools. You download a zip file from the releases page, move the app to your Applications folder, and approve it in System Settings on first launch because the app is not code-signed through Apple's notarization service. The app requires macOS 14.4 or newer and works on both Apple Silicon and Intel Macs. A few limitations are noted in the README. Volume settings are not saved between sessions, so sliders reset to default each time you quit and reopen the app. Controlling individual browser tabs separately is not possible, because the browser mixes all tabs into a single audio stream before macOS can see them, a per-tab browser extension would be needed for that use case. Per-app output routing (sending one app to speakers and another to headphones) is also not yet implemented. Source code is available under the MIT license and can be built from source with Xcode or the Xcode command-line tools.