How to turn off the sound in the Android application if there are no internal settings?

Question

Google

There is a game called vainglory. It doesn't have any settings at all.
PURPOSE: I want to play while listening to my music from the player, and cut off the sound in the game.

Answer 1

Try Xposed with the appropriate Android module (doesn't work with ART runtime at the moment).
This will probably help you.

Answer 2

On the phone, cover the speaker with chewing gum, and put music on the player.