I looked into this about a year ago...each phone seems to support different incompatible formats, but many of these are just plain ascii text files (especially monophonic ringtones). There seem to be a lot of tools to take midi files and convert them to something a phone will understand. Who knows, maybe phones play midi files these days as well.
I gave up on my project to work on my undergrad thesis...best of luck though.
― Silas Beauford (Silas Beauford), Monday, 26 April 2004 17:54 (twenty-one years ago)