Guide · Updated
The notch equalizer: hearing the music or just dancing
Short answer. Nearly every notch app draws bouncing bars next to the album art. Often it's just an animation: the bars move the same way to any song, even on pause. A real visualizer has to listen to your Mac's audio — since macOS 14.2 that's done with Core Audio taps and the system audio recording permission. Going by their code and developers' descriptions, Atoll, Notchy and SparkU listen to the sound, while Boring Notch draws random heights.
How to tell real from animated
Play a track with a quiet intro, then a loud chorus. A real visualizer:
- freezes on silence and on pause;
- moves the left bars on bass and the right bars on cymbals;
- hits the beats instead of swaying to its own rhythm.
An animation moves the same way to any music, at one speed. That's not a trick: it's simpler and needs no extra permission. But if you want to see the music rather than a decoration, the difference is obvious right away.
How an app hears your Mac
There are two ways:
| Method | Since macOS | Permission | What else the app gets |
|---|---|---|---|
| Core Audio taps | 14.2 | System audio recording | Audio only: one player or all of the Mac's sound |
| ScreenCaptureKit | 13 | Screen and audio recording | Technically, the screen too |
System Settings → Privacy & Security has a "Screen & System Audio Recording" section. Per Apple's guide, you can allow an app to record both your screen and audio, or just your audio. A visualizer only needs the audio.
An app that asks for screen recording for its equalizer gets permission for more than it needs. That alone doesn't mean it records anything, but choose deliberately.
Which apps listen to the sound
| App | Visualizer | Based on |
|---|---|---|
| Atoll | Real | Its open source code uses Core Audio taps |
| Notchy | Real | The developer says: a spectrum of system audio via a Core Audio process tap |
| Boring Notch | Animation | In its open source code the bars get a random height three times a second |
| SparkU | Real — opt-in | Core Audio taps, details below |
| Alcove, NotchNook, Seam, MacNotch, Droppy | Not stated | Their official pages don't say |
How SparkU does it
Animation by default. Right after install, SparkU listens to nothing and asks for no audio permission.
Real audio is opt-in. Turn it on in the player settings, and macOS asks once for "Audio Recording". SparkU doesn't need screen recording.
Then:
- SparkU listens only to the player that's currently playing, or, if that fails, to all of the Mac's audio.
- The sound is split into four bands right on your Mac, and the bars follow them.
- No audio is recorded or sent anywhere. Listening only runs while something is playing.
- If anything goes wrong — the permission is revoked, the player quits — the island quietly falls back to the animation.
There's a second option too: the island glows to the beat.
Where we're weaker. SparkU isn't out yet: it launches in spring 2027, in beta now. The player works with any app that tells macOS what's playing, but the extra Spotify, Apple Music and YouTube features are still in the works.
FAQ
Why does a notch app need audio recording permission? So the visualizer moves to the actual music. Without it, the app doesn't know what's playing and can only show an animation.
Does it record my calls? The permission lets an app hear your Mac's audio. An honest app processes it on the spot and keeps nothing. If in doubt, pick an open source app or keep the animation — it's the default in SparkU.
Why does the visualizer move when the music is paused? Then it's an animation, not real audio.
Does this need screen recording? Not since macOS 14.2: Core Audio taps capture audio only. If an app asks for screen recording, it most likely uses ScreenCaptureKit.
Sources (as of October 15, 2026): Apple — capturing system audio with Core Audio taps, macOS guide on screen and audio recording; source code of Atoll and Boring Notch; Notchy's website.