Stopping and playing a sound while code executes

So I have a pretty complicated problem at the moment. What I want is to be able to play some music when a certain mob is detected. The problem with this is that I check if the mob is being detected every tick and therefore, the sound resets every time it gets to the playsound function (once a tick as long as the mob is still withing loaded chunks). This results in the music playing over and over again instead of stopping only when the mob is no longer within loaded chunks. So I know I can fix this by using a boolean variable to tell whether or not the mob is there, but I have no clue how to stop the playsound function once it starts. I really don't want to have to implement threading into this mod because I don't know how to do that and it would make things way more complicated than they need to be, so if anyone can help that would be awesome.