As pre-announced at last week’s The Beat Goes On event in San Francisco, Apple has today turned on custom ringtone functionality in iTunes. The feature enables users to convert certain iTunes Store tracks into ringtones at a cost of $0.99 per ringtone plus the initial cost of the iTunes Store download; other tracks, including ones you have imported from your own CDs, cannot be converted.

To support the feature, a new “Ringtones” area has appeared in the Library column on the left hand side of the iTunes screen, and there is now an option to “Create Ringtone” from eligible tracks. In addition, users can now add the “Ringtone” column in the View Options (Command-J) box.
Doing so brings up a message stating “You can create iPhone ringtones from many songs purchased from the iTunes Store. Do you want to check with the iTunes Store to see which songs the music labels have cleared for use as ringtones?” Underneath this message explaining that users can click the bell next to cleared songs to create a ringtone.