There is a music writing a program called Sibelius which can can take sampled sound and turn it through midi into sheet music, then through it's add on program can scan sheet music and turn it into midi which then can be stored as mp3. So it might be possible to to do mp3 to midi. 8l1nd 8l1nd
I will check it out tomorrow with a mate who is a "clever bugger" and get back to you.