music wouldn't stop playing

yesterday my phone was sitting on the table and the music just started playing from my library.  it wouldn't stop and i couldn't turn it off i had to turn the phone off.  in the future how do i turn the music off, even if i play a soung i dont see a stop button.   wow!!!!

i am not runniny any security apps and that could of been the problem.  what is a good app to download for security thanks.

I know this is kind of an old post, but I think I found why this happens in the Android Devices. 

I had an SD Card go bad, and the backup files I had on my computer were kind of old.  When I re-installed the new SD Card, it didn't have all the sound files on it that I had used to set certain ringtones and what not.  So in replace of what WAS there, it started playing a certain MP3 track that I had loaded onto the phone in place of the old ringtone in error.  Once I reset the ringtones to what I had available, no more problem with the phone playing tracks all the sudeen.