You can't turn down music or video volume without also silencing system notification sounds
You're watching a video at low volume and every notification ding is also barely audible. Or you crank up the volume for a video call and now every email notification blasts you. System sounds and media volume are glued together with no way to separate them natively.
Why does this happen?
macOS routes system alert sounds and media audio through the same output volume control. Unlike Windows, which has per-application volume mixing built into the OS, macOS treats all audio output as a single stream.
How to fix it
System Settings → Sound → set Alert volume separately from the main output volume slider.
For full per-app volume control: install BackgroundMusic (free, open-source) or Boom 3D which adds per-app volume mixing.
In practice, many users mute notifications during focused work: System Settings → Focus → Do Not Disturb.
Discussion
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