Here is a very common use case I have: I listen to music on Spotify while going through my Facebook feed. Sometimes there's a video that I want to see in full screen. When I tap the video, music playback stops. What I want is to watch the video without any sound and keep my music playing. Is that possible? Phone: Galaxy S8
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I don't think it is possible under normal circumstances for speakers can not be controlled by multiple apps simultaneously. – SarpSTA Sep 7 '17 at 3:02
You can't do this exactly, But there's a workaround. Go to settings > sounds & vibration > sperate app sound. Note: that this will only work if a Bluetooth device is connected.