Spotify stops when I enter a game?

[CFood]

Every time I go into Fire Emblem Heroes, the game in question, Spotify stops.  How do I stop this?

I keep entering and exiting Fire Emblem and Facebook to talk about the game, and the music keeps stopping. I'd like the music to keep playing when I enter the game.  Which I keep muted so it shouldn't stop Spotify, right? 

I'm on Android 5.1.1 Sony Xperia Z3v.