Samsung has included a number of useful audio settings in its Galaxy smartphones, one being Separate App Sound. This feature allows you to stream the sound from one of your phone's apps to a Bluetooth speaker or headset, all the while your smartphone continues to make whatever sound it’s making -- a voice call, or playing sound from a different app.
How could I use it?
As an example of its usefulness, I was able to watch YouTube on my smartphone in one room of my house, while simultaneously streaming a podcast to family members in another, freeing up another device for my kids to use in the process. I could also run my navigation app on my smartphone while playing music from my Spotify app on another Bluetooth device, without the music being incessantly interrupted by the navigation commands.
Samsung devices with Separate App Sound
You’ll find this feature on the latest Samsung smartphones, including the Samsung Galaxy S20, Samsung Galaxy S21 and on most Samsung smartphones released with the Android 7.0 (Nougat), or later operating systems, including the current Android 11 OS.
How to separate app sound
1) Tap Settings > Sounds and Vibration > Separate App Sound.
2) Tap the switch to turn it on.
3) Now select the multimedia app you would like to stream to a different device. It may be included in a list of apps already shown. If the app you want doesn’t appear, press Add apps and select it.
4) Select the audio device you would like your app to be connected to. Note: only connected Bluetooth devices will be shown in the list of devices you can choose.
And that’s all there is to it. The app you selected will now play its sound through your selected Bluetooth device or headset, while any other app you launch will be played from your phone's selected audio output device.