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.
Get Sound in v1.0.0
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, EQ, and output routing for that process.
- Download Semper v1.0.0 for macOS 15.4 or later.
- Open the disk image and drag Semper into Applications.
- Launch Semper and 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.
You can also install the published release with Homebrew:
brew install --cask niharnm/tap/semper.
The v1.0.0 download includes Sound only. See the
module overview for the other utilities
in development, or build the current source.
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
- Per-app audio control requires macOS 15.4 or later.
- 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.
Open Sound in a source build
Source builds include the integrated module interface and development utilities. They differ from the v1.0.0 download. Follow the repository's build instructions to build and run the Semper scheme in Xcode.
git clone https://github.com/niharnm/Semper.git
cd Semper
open Semper.xcodeprojOpen Semper from its menu bar icon. From Home, choose Sound, then Open Sound to start its audio controls and grant the requested audio access. Browsing Home does not start audio capture. The source-build module guide explains adding modules, their controls, and action search.
The public repository contains the app, Core Audio engine, tests, setup guides, issue tracker, and contribution rules. See its licensing information and notices.
Open Semper on GitHub