Stop FaceTime from answering a call with Play/Pause button F8
Solution 1:
This has been driving me nuts for a long time. It's not an ideal solution but if you open FaceTime and go to Preferences, there is a check box for Calls From iPhone. The description reads, "Use your iPone cellular account to make and receive calls when your iPhone is nearby and on Wi-Fi."
If you uncheck that box when you receive calls your Mac will no longer try to answer the call, leaving the play/pause button to control your music only.
I would have preferred that when I get an incoming call and I press the play/pause button that my music is paused and the call was answered, but until this is fixed, the solution above was the best I could come up with to end the insanity of music playing and phone call coming in at the same time.