take a program like this
Audacity: Free Audio Editor and Recorder
and take any mp3 and make your ringtone
then find an mp3 to midi or wav to midi converter
MP3 To MIDI Converter - MP3 To MIDI,MP3 Mid Converter,MP3 2 Mid,Audio To MIDI
then you can email to your phone
xxxxxxxxxx@vzwpix.com as the email addy with the x's being your 10 digit number
ur phone should receive as an mms
this should give you a basic idea how to
you most likely will Not find a website that conveniently does this for you
and if you do it wont be free.
but the tools should be available for you to do it yourself free
i make all my own ringtones in a similar manner like this