I think `MusicComms.mrc` should be a private variable in `MusicComms`, and we shouldn't access it here. We could do one of two things:

1. Add a property called `MusicComms.enabled` that starts out false and gets set to true when we call `MusicComms.init()`
2. Have `MusicComms.notifyMetadataChanged` and `MusicComms.notifyStatusChanged` just do nothing if we never initialized `MusicComms`