The music at the Oshu'gun crystal in Nagrand is from Mozart's opera The Magic Flute

This is awesome, music in WoW is something I've never even really thought about as far as outside sources or references go. I am not a big opera buff, but my dad played that one in particular a lot when I was little, so I have listened to it a lot since. That made the melody stick out like a sore thumb.

• Oshu'gun music
• Aria: O zittre nicht, mein lieber Sohn 

Bonus info: the Honor Hold music is from Chopin's Nocturne in C# minor, Op.27/1? It's beautiful.

• Honor Hold
• Op.27 1 Rubenstein

For what it's worth, the Lisitsa interpretation is pleasing too.
Blizzard really went ham on the opera when they were laying down the Outland tunes didnt they?!