Well a friend of mine went for a sanity interview a few years back, they just sat in a group and asked why you want to work there etc..
my advice is be creative in your answer, everyone is going to say ' i have a passion for music ' or ' I play guitar/piano etc' , try to make your answers stand out...
maybe even have a couple of artists/albums/movies/tv shows you like just in case they ask you about it, its always good to have a look around on the companies website, 10 minutes of browsing could make a difference in the end.
If they make you do any group activities just don't dominate the conversation, but at the same time don't be completely mute.
Make sure you dress appropriately of course, smile and be yourself!