If you are using Skype for Business, possibly also standard Skype, you might appreciate the fact that it reduces the volume of other apps like Spotify etc when there's an incoming or outgoing call.
A problem I have in Windows 10 is that the sound is reduced, but when the call is over the volume is not reset properly. I've found that I can go to the volume mixer and adjust the volume of the muted application, but often when I then change the overall sound volume, the apps volume is reduced again.
Luckily there's a solution. While not perfect, it stops the annoyance of Skype not unmuting sound properly.