are polyphonic ringtones just midi files?
 

:)

I believe they are :)

Yes...almost! Just a lot less channels (depending on the phone).

Nokia suite will convert midis to polyphonic tunes for nokias. Just a matter of selecting which channels to delete and which ones to keep (IIRC nokias only have 3 or 4 audio channels...General midi is up to 16 channels and 24 voices)

my Sony Ericcson T367 certainly uses midi files for it's polyphonic ring tones. I have a rather nice little utility to download files from it, so aquired the normal ringtones, plus added my own, all of which are midi files.