Ringtones

A ringtone is an AAC audio file under 40 seconds with an extension of .m4r.

Official and package-distributed ringtones are stored in the /Library/Ringtones folder, while ringtones synced from iTunes are located at ~/Media/iTunes_Control/Ringtones.

The "Marimba" ringtone is an exception: it is always located inside of SpringBoard.app as /System/Library/CoreServices/SpringBoard.app/ring.m4r.

Ringtones can be used as the alert sound for incoming phone calls, alarms or the countdown timer. Since iOS 5 beta 4, it is possible to use them as alert sounds, thereby providing a semi-official way to customize the sound of Voicemail, SMS/MMS, Mail, Calendar and Reminders alerts.