The American electronica musician Adam Young of Owl City has revealed on his discography page that he created at least some of the new system sounds in iOS 7. Under "Artist" Young lists "Apple" and under "Year" and "Label" Young lists "2013" and "Sounds for iOS7."
Besides completely remastering virtually all of the previous iOS's system sounds, many new ones were introduced, including a number of ringtones and system alerts. It's not entirely clear if Young created all the new iOS 7 sounds, or just some of them.
As 9to5Mac points out, what is really interesting/impressive is that some Owl City fans had
