Motorola MPx220

From my experience, it has worked, but it seems to cause Error messages and malfunctions. I had more success with recording a short wav file that is formatted the same as one of the ringtones that came on the phone. For instance, open the barking ringtone, record something else over it, and save it to a different name. It seems to keep the same settings as the barking ringtone and does not error as much.
That's just something I tried and I cannot guarantee it will work. I have pretty much given up on this phone.