Way to modify Contact's ringtone via ABPerson class iOS?

Question

So I've been toying around with the AddressBook framework on iOS and have noticed in the ABPerson class, pretty much every attribute of a contact is listed as a constant (ref: apple documentation). However, one attribute I notice is missing is the ability to make a custom ringtone. Is there any way to modify the ringtone of a contact via the ABPerson class? If not, is there any way at all to modify the custom ringtone using the AddressBook framework? iOS 5.1.1.