Thanks for the details 
Do you have a way to modify this custom API?
This custom API could return an integer instead of a string, which would also match the native music features we currently have in Gladys:
Using these native features would also let you use the player on the dashboard with your MPD server:
Ideally, if you can modify the custom API to send state changes via MQTT to Gladys, that would allow you to have the music widget always up to date on your dashboard
If this is something that works for you, I can walk you through the entire procedure! And honestly, I think it’s a better solution than using a string that doesn’t correspond to anything in Gladys