Basically, audio -> MIDI conversion is not an easy or simple process, because a standard MIDI file is not a sound, it's a sequence of instructions to another sound-generating device, like a synthesizer or the sound chip in your phone. So I think you're outta luck with these files.
You can get quite creative with MIDI, but it's a lot of work, and how good it sounds is limited by the hardware. e.g. the "piano" in some phones is a Longway from a Steinway.
