nodejs plugin had a open folder type thing to have an app to load external audio on request and let users select their "audio" for specific reasons.
in ur case thats what im thinking u want.
i used it also for making a "winamp" clone.. worked fine for desktop, when i wanted to import "music" into a playlist.
not sure how and if you can use nodejs export plugin thing for hosted games on browsers tho...like the HTML5 thing, but u can use html5 / javascript to do the same thing.
you just code the same as you would in a web aplication in the script part.
hope it helps.