On your Andriod phone, when you can't see the music playing, on the lock screen. All you need to do is go to your phone settings and enter 'Apps & Notification' click on the music app, tap on the data usage and then clear your cache.."IT'S DONE"... That's all you need to do. It's pretty simple right?
But you should only do this if you don't care about your playlists anymore, cause as you clear your cache it removes all the playlists you've created from your music app and then your songs will start showing on the lock screen again.
NOTE: please do not clear your data usage, ONLY CLEAR YOUR CACHE because you may lose all your songs.