Computer sound from remote computer is muted when voice call is entered

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I'm connecting to a friend's pc, both running Windows 10. The computer sound from his pc transmits fine when the "use computer sound" box is checked, but as soon as we enter into a VOIP call through teamviewer the computer sounds stops being transmitted.

Is this normal?

Please help if you can, we just want to be able to play a game together while voice chatting without one of us having to deal with echoing voices via skype or discord.