Samsung SM-G950W User Manual page 110

Apps and features
Controlling music playback when the screen is off
You can control music playback when the screen is off, without turning on the screen.
1
Launch the Settings app, tap Lock screen and security → Information and
FaceWidgets → FaceWidgets, and then tap the Music Controller switch to activate it.
2
To control music playback when the screen is off, double-tap the clock.
3
Tap the icons to control the playback.
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