If you want to send a ringtone to a phone, or to add a ringtone to the library, then you need to upload the file on the website.

Midi files are created using software programs like CubasisGo. Midi files have a .mid file extension and are not "human readable"

RTTTL and RTX files are simple text files and they can be edited for example in "Word". Here is a ringtone in RTX format
"Adams Family:d=4,o=5,b=160:8c,f,8a,f,8c,b4,2g,8f,e,8g,e,8e4,a4, 2f,8c,f,8a,f,8c,b4,2g, 8f,e,8c,d,8e,1f,8c,8d,8e,8f,1p,8d,8e,8f#,8g,1p,8d,8e,8f#,8g,p,8d,8e,8f#,8g,p,8c,8d,8e,8f"

RTTTL and RTX files can only describe limited musical capabilities which is quite appropriate for today's monophonic mobile phones.

Midi files can describe a whole orchestra of instruments so midi composers are used by musicians and will be required to write ringtones for tomorrows polyphonic phones.