A macOS menu bar app that replaces the default volume key behavior with enhanced volume control, built as a lightweight wrapper around CoreAudio.
BigVolumeKeys intercepts the system volume up/down/mute keys and routes them through CoreAudio directly, giving you finer-grained control over your output devices. It's especially useful for multi-output (aggregate) audio devices, where macOS's built-in volume keys often don't work at all.
Key features:
- Logarithmic key ramping -- tap for small increments, hold for accelerating volume changes
- Multi-output device support -- control all sub-devices of an aggregate device simultaneously, with a master slider that preserves relative balance between outputs
- Per-device sliders -- adjust individual sub-device volumes independently
- Manual device addition -- add output devices that aren't auto-detected as sub-devices
The app sits in your menu bar and uses a CoreGraphics event tap to intercept volume key events before macOS handles them. It then translates those key presses into CoreAudio API calls (AudioObjectSetPropertyData with kAudioDevicePropertyVolumeScalar) to set volume directly on the output device or its sub-devices.
For aggregate/multi-output devices, it queries kAudioAggregateDevicePropertyFullSubDeviceList to discover sub-devices and controls each one individually -- something macOS doesn't do natively with the volume keys.
The app requires two macOS permissions to function:
- Accessibility -- to create an event tap that intercepts volume key presses
- Input Monitoring -- required by macOS for event tap creation
The app will prompt you to grant these on first launch, and auto-starts interception once both are granted.
- Swift / SwiftUI
- CoreAudio for device enumeration and volume/mute control
- CoreGraphics event taps for key interception