No because polyphonic ringtones use the MIDI format of up to 16 tones being played simultaneously - ie polyphony. The monophonic entry of notes on phones was straightforward enough to be able to be included as an editor in the OS of most phones. If you have a Nokia you can use Nokia's PC Suite software to convert general MIDI files to scalable polyphonic files which you can then port to your phone vie Bluetooth or data cable.
Not sure if you can create polyphonic tones here but you can create something !! You can also download tones for free (well just the cost of the time you are WAP connected)