The event sold out within two hours, making WWDC the tech world’s version of a Taylor Swift concert. Today at Apple’s keynote, the “Royal Wedding for nerds,” Apple announced iTunes Match, its new music service.

All iOS devices will include “Automatic Downloading,” a simple switch that will automatically download all of your iTunes songs to your devices when purchased in the iTunes store. You can use this service to automatically download songs on up to 10 other devices, for free.

“This is a first in the music industry,” said Apple’s Steve Jobs.

iTunes Match will automatically scan your library and allow you to download all of your music to iTunes, even songs not purchased through the app store. iTunes Match costs just $24.99 a year, which beats both Google and Amazon’s offerings. See this chart below to compare how Apple stacks up against other music services:

For a complete run-down of today’s announcements, see our post: Everything you need to know from WWDC 2011 in one handy list