Music suddenly playing on ipad 3 with ios 8.3

I have an iPad 3 with iOS 8.3. Whenever I have my headphones plugged in and am watching a show on my HBO app, music will suddenly start playing from the music app. I double cluck the home button, but it shows the only app running is the HBO app. I opened the music app, and it shows that music is playing. I stop the music, close the app, go back to watching my show, and after some time music will start playing again. Why is it doing this, and how to I stop this?