iPad playing a song with no apps open

I have an iPad not sure which kind but every so often it will play a specific song. I don't know how to stop it and all I can do when it happens is shut down the iPad as a whole. It is not a song I have heard or downloaded and the first time it happened, I checked Spotify (my music app) and it said it wasn't playing something, so I closed my apps and it stopped. This time, instead of it stopping when I closed my apps, it kept playing and I had to shut off my iPad. If anybody knows what's happening or how to fix it, reply to this