How do I turn off background music on Moto X when using the phone?

[AC Question]

My wife's Moto X started playing background music when she uses the phone (for a phone call). She does not know how it got turned on, and it's pleasant music, but we need to turn it off. Does anyone know how to do that?

Thanks!

 

[Golfdriver97]

Maybe it's in call settings somewhere? This is the first I have heard of it.