I would go with Theatre, although losing Music would be very sad.

But actually, how does Brentus define Theatre? What about opera and ballet? I am going to see an opera today and I love ballet. If you count them as Music rather than Theatre, then I would go for Music.

Q: if a Martian extraterrestrial arrives and inquires from you about life on Earth, how would you explain what Bipolar illness is to them in simple, accessible terms?