Let’s say you are using
How can I do it on Windows?
Right-click on the little speaker icon in the system tray and choose Sounds.
It opens up the Sound dialog box. Switch over to Communications and select “Mute all other sounds” option.
Click OK. And you are all set.
It sounds just that simple. But one more thing.
Let’s switch back to Playback tab, and set Default Device and Default Communication Device to the one that plays background music, not the one used for the softphone.
This is actually pretty important. Unless you are using one device for both music and communication, you will make sure the default device and default communication device are set to the same device.