has_many_polymorphs - specifying the names of the 'children'

I have a class called MusicService which can have various things 'shared' with it, so i'm setting up a has_many_polymorphs like this:

has_many_polymorphs :shared_content, :from => [:resources, :lessons, :courses], :through => :sharings

However, this will generate some associations like this:

@music_service.resources => resources shared with that music service.

However, i don't want that association as it already exists and has a different meaning ('resources created by that music service'). So, i want the polymorphic associations to be called

@music_service.shared_resources @music_service.shared_lessons @music_service.shared_courses

Similarly, i want to refer to the music services that have been linked through sharings as 'allowed_music_services', so

@resource.allowed_music_services @course.allowed_music_services @lesson.allowed_music_services

I'm sure this is simple but i can't work it out, can anyone help please?

thanks max