Guys, it is impossible to get a perfect conversion of .mp3 to .midi.
MIDI stands for Musical Instrument Digital Interface. Basically, a midi file is like a sheet of music: it contains the tones to be played an the instrument that should play them, but does not contain the actual sound. The computer/cell phone/whatever is playing the file has to look the instruments up in a table and process the sound itself.
Mp3, on the other hand, contains the sound only, not the notes that make up the sound. It is the actual recording. The mp3 file is the recording of a sound; the player couldn't care less about what it is playing.
Software that tries to convert .mp3 to midi tries to guess at what instruments play which tones and encodes them in a score. I have tried some of it myself, and the results were not good. The simplest piano piece with no other instruments playing could never be said to have come from the original.
ALL individual nuances are lost/never actually present in a midi file. The computer will play the SAME note, at the SAME pitch, with the SAME characteristics, EVERY SINGLE TIME. A particular instrument or voice has much more variation and uniqueness to it. That's why midi files sound all too perfect - they are nothing but a robotic parody of what the song should be. Sure, a midi program could play Chopin's "Polonaise in A Major" technically perfectly, but a human performance would have expression, love, emotion, and variance infused into the piece.
Sorry if I've gone on and on and on....... I just think the impossibility of this proposal could be seen obviously with a basic understanding of the two file formats.
David
EDIT: If you would like to see what I'm talking about, take a look at the midi file offered here:
My Chemical Romance - Welcome to the Black Parade
It's "Welcome to the Black Parade" by My Chemical Romance. Have a listen to that, and then go listen to the real song or at least the sample on iTunes. You'll see that the .mp3 blows the mid out of the water; the mid is, at best, a primitive guess at what notes are in the song.