Inside SoundTune: A Volume Slider for Every App
A Mac has one volume for everything. Turn the music down and the call gets quieter too; turn the game down and so is everything else. macOS has never shipped a fix for it. SoundTune is a small utility that lives behind a fader icon in the menu bar and gives every app its own slider, for $19, paid once. This teardown walks through it screen by screen. If you came for the engineering, skip to How it works underneath.
A mixer under the menu bar
Clicking the icon opens a panel with two sections. Output lists the devices the Mac can play through, each with its own volume, and Apps lists everything currently making sound. Every row is the same shape: an icon, a name, a mute button, a slider and a percentage.
App icons are drawn in greyscale so the panel stays black and white like the rest of the 1dot1 apps, and so the eye goes to the sliders rather than a row of colourful squares.
One slider per app
Each slider runs from silence to 200%. Below 100% the app is quieter than the rest of the system; above it, louder. Volumes are remembered per app, so a browser that is always too loud stays where it was put, and a quiet meeting app opens boosted.
Only apps that are actually playing, or that have a volume set, appear in the list. Helper processes are folded into the app they belong to, so a browser shows once rather than three times, and background daemons stay out of the way until they make a sound.
Mute one, keep the rest
The speaker button beside each slider mutes that app alone. It is the fastest way to deal with a game or a video that starts shouting during a call, and it beats pausing the app because the app never knows: it keeps playing, it is simply not heard.
A right-click on the menu bar icon mutes every app at once and changes the icon to show it, which suits the moment someone walks into the room. A second right-click brings everything back at the levels it had.
Outputs in the same panel
Switching output usually means a trip to System Settings or a modifier-click in Control Centre. SoundTune lists the outputs at the top of the same panel: click a name to switch to it, drag its slider for the device volume, or mute it outright. Devices appear and disappear as headphones connect.
Turn a quiet app up
Boosting past 100% is where a per-app mixer earns its place. A recorded meeting with a quiet speaker, a video with weak audio, a game that mixes its dialogue too low: all of them can be lifted without touching the system volume and blowing the ears off everything else.
A limiter sits at the end of the chain, so a boost squashes the loudest peaks instead of clipping them into distortion.
How it works underneath
macOS has no general setting for per-app volume, so SoundTune uses the audio tap support Apple added in macOS 14.4. For each app being adjusted, it asks macOS for a private tap: the app's own output is muted and its audio is handed to SoundTune, which plays it back at the level chosen. A private aggregate device holds those taps alongside the real output device, and one callback mixes them together.
Two details matter for sound quality. The mixer runs at the sample rate the app is producing, because playing 48 kHz audio through a 44.1 kHz stream sounds slowed down and robotic. And apps at 100% are never tapped at all: their audio takes the normal path, untouched, so SoundTune only sits in the signal path when it has something to do.
That also explains the permission prompt. Handling another app's audio is exactly what macOS guards with the system audio permission, so it asks the first time a slider moves. Nothing is recorded, and nothing leaves the Mac.
Built in black and white
Like the other 1dot1 Mac apps, SoundTune is greyscale in light and dark mode. The icon is three faders with their knobs at different heights, and the menu bar icon repeats the same shape at a smaller size, with a slash through it while everything is muted.
It is a universal app for Apple silicon and Intel Macs and needs macOS 14.4 Sonoma or later. There is no account, no tracking and no audio driver to install.
Get SoundTune
SoundTune is $19, paid once — not a subscription, and no renewal to forget about. It is a single download with a README and the licence inside the zip. For context, SoundSource is $49 and does considerably more, including an equaliser and plugin support; if you need those, buy that one instead. If all you ever wanted was a volume slider for each app, this is the cheaper way to get it.