How do I disable audio pause in Android 5.0 when receiving notifications?
If you're willing to switch to another audio player than whatever you're currently using, you can achieve this with PowerAmp. It has a menu for audio focus, which has settings for pausing or not when a notification is received, and whether to pause or not when there's an incoming call.



The one I linked to is the trial version. The pro version costs roughly $5.

I'm not directly affiliated with MaxMP or PowerAmp, but I am betatesting the upcoming version.