Facetime call START Spotify playing on my mac

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Plan - Premium

Country - US

Device - Mac Pro 2011

Operating System - High Sierra

For some reason, whenever a Facetime calls comes in, my Spotify on my Mac starts playing music. Yes, starts. 

As I understand it, the functionality should be exactly the opposite, with everything pausing as the ringing begins.

I've also noticed it happening with a YouTube video I have paused in a browser.

So you can imagine the cacophony that ensues when I receive a call:

 The ringer kicks off, Spotify starts playing music, and some random YouTube video starts playing. 

Any suggestions would be greatly apprecaited.