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.