There is a major bug in this plugin - if you unlock tracks (with their switches) in an order outside of the order they are listed in the plugin parameters (ie unlocking track 1 and then track 3 without track 2 first), the songs wont play until you also unlock the other tracks listed before them. I'll try sending an email with a demo project file with this bug. Atm, it is making the plugin unusable for my game.
Viewing post in RPG MAKER MZ Plugin: Music Media Player comments
I have released an update to the plugin, hopefully that solves the problem, I made the modification directly from your demo to make sure it works, but just in case I want you to try it yourself.
I have deleted the link you attached. Remember not to expose the projects publicly since they contain paid content and anyone could access them.
All the best!