How to output sound through my TV when using airplay to extend my desktop?

I've updated my software to Mavericks recently, and love the 'extnd desktop' feature, with exception for one flaw: all the sound still comes through my measly macbook speakers. I dragged the Pandora app to my extended desktop (i.e. my tv) in hopes that it would come through my TV speakers, but that wasn't the case. I tried going to sound preferences from my macbook to change the sound output from "internal speakers" to "apple tv", but for some reason it simply doesn't let me when I click on apple "tv".