Direct answer
Mac users can change overall output volume in Sound settings and use any volume control an individual app provides. macOS does not include one built-in mixer with independent sliders and output routes for every app. A process-tap utility such as Semper can add those controls.
What macOS provides
Apple's Sound settings guide documents output-device selection, one output-volume slider, mute, and balance. Apple also notes that an app's own volume control cannot exceed the Mac's selected output volume.
Audio MIDI Setup configures devices, sample rates, channel formats, and aggregate devices. Apple's Audio MIDI Setup guide does not describe a system-wide per-app volume mixer.
How Semper adds per-app volume
Semper identifies processes that are producing audio and creates an independent signal path for each one. The menu-bar popup then controls gain, mute, boost, balance, EQ, and output routing for that process.
- Clone the public repository and open the Xcode project.
- Build and run the Semper scheme on macOS 15.4 or later.
- Grant Screen & System Audio Recording permission when macOS asks for it, then relaunch Semper.
- Start audio in an app so it appears in the mixer.
- Adjust that app without changing the other app sliders.
git clone https://github.com/niharnm/Semper.git
cd Semper
open Semper.xcodeprojSemper has no packaged public release yet. Building from source is the only official way to run it today.
Route different apps to different outputs
Each app can follow the current system output or use another available device. A call can use AirPods while music uses a display or USB interface. Semper remembers explicit routing choices and checks the capabilities of each output device.
Hardware behavior differs. Bluetooth headsets, HDMI displays, USB DACs, built-in speakers, and DDC-capable monitors do not expose the same controls, so Semper hides controls that the current path cannot apply.
Why Semper needs audio permission
Screen & System Audio Recording permission authorizes the Core Audio process taps used for per-app control. Semper processes tapped audio in memory and does not intentionally save or upload it to the project maintainers.
Microphone permission supports input-device monitoring. Accessibility permission is optional and supports media-key control. Read the privacy policy for the full data-handling details.
Known limits
- There is no signed public DMG or stable release yet.
- Apps with custom audio engines can react badly to process taps. This can include some DAWs, calling apps, and audio tools.
- Only apps actively producing audio appear in the default mixer list.
- Device volume and routing support depends on the hardware and transport.
The repository troubleshooting guide covers permissions, missing apps, routing, media keys, and audio quality.
Read or build the source
Semper is published under GPL-3.0-only. The repository contains the app, Core Audio engine, tests, setup guides, issue tracker, and contribution rules.
Open Semper on GitHub