playing recorded music/sounds while doing other things on phone

Hey I'm new to this forum but i found out something interesting today about recorded sounds. I was listening to some music i recorded on my phone and noticed i could keep the music playing if i paused it, then pressed play and quickly after that press the back button on the phone at bottom middle that the music/sound would start playing and you could do anything you wanted on the phone w/o it pausing the recorded audio. Is this a glitch or has anyone else found this out?