SonicFlow
macOS still doesn't let you control the volume of individual apps — if Spotify is loud, Zoom's ringtone hits you at the same level. SonicFlow is a free, open-source menu bar app that gives you an independent volume slider for every app currently making sound. Plus auto-ducking: when someone speaks on a Zoom or Teams call, your music automatically lowers.
Built in Swift 6 with CoreAudio Process Taps (the new low-level API Apple shipped in macOS 14.2). Under 1% CPU, MIT licensed, no telemetry. Just download the .app and drop it in your menu bar.
I built this because I got tired of Slack and Zoom shouting over my music. Apple ships per-app volume on iOS but not macOS — there's no public UI for it, even though the low-level APIs exist. SonicFlow uses those APIs (specifically AudioHardwareCreateProcessTap, available since macOS 14.2) to give every app an independent slider.
A few details that might be useful:
Free and open source (MIT). No paid tier coming.
Under 1% CPU, lock-free realtime audio path, allocation-free IOProcs.
No microphone permission requested — Process Taps are output-capture, not input. The purple dot never appears.
Works alongside your existing audio setup — doesn't change the system default output, doesn't install a virtual driver, doesn't require a reboot.
If you've used SoundSource: SonicFlow is a much smaller open-source alternative focused on the per-app-volume use case. SoundSource is still the right buy if you need EQ, audio routing, recording, etc.
Code & roadmap: [https://github.com/altuzar/sonicflow](https://github.com/altuzar/sonicflow)
Looking forward to your feedback. Happy to answer technical questions about the CoreAudio side (it was a rabbit hole).