Make sure you correctly ask for and release Audio Focus as described here:
http://developer.android.com/training/managing-audio/audio-focus.html
With multiple apps potentially playing audio it's important to think about how they should interact. To avoid every music app playing at the same time, Android uses audio focus to moderate audio playback—only apps that hold the audio focus should play audio.
Basically this allows the framework to handle interrupts properly as you cannot specifically code for every situation.