Short answer is you cant. Think of an mp3 as a recorded act of music, and a midi as a piece of sheet music. The only way to convert would be to listen to the mp3, and create a midi from what you hear.
There are things called pitchriders that can convert a simple sound like a single guitar string or a note from a Clarinet into a midi note number, but these are simple waveforms. An mp3 recording of a song is a very complex waveform which would confuse a pitchrider.
A person can convert a MIDI to an MP3 by Zamazar. This is an online conversion program that is available for free.
Just Export as MIDI file.. Then, convert MIDI file to Mp3 file.
IntelliScore Polyphonic WAV to MIDI can you use to convert mp3 to midi. But the demo only lets you convert the first 15 seconds.
FL Studio can import MIDI files and export WAV, MP3, OGG and MIDI files.
In order to convert AMR files to MP3 files, you will need to purchase an audio converter. There are several free ones online and available for download.
Use google and search for midi files or instrumental mp3's.
The easiest way to convert your files to mp3 is to download a file converter off of the internet. I found a great converter at www.maniactools.com/soft/m4a-to-mp3-converter.
Try www.convertit.com
Audacity is a program that allows you to record and edit sound files. Additionally, the Youtube Downloader is able to convert files from .wav to .mp3, and even convert video files into sound.
http://myrightbrain.wordpress.com/2006/06/11/how-to-convert-mp4-audio-files-to-mp3-using-itunes/ There, follow the instructions and convert it. Or you could look at some programs.
CNet has a free software that allows users to convert FLAC files to MP3 files, whether for use on an iPod or on iTunes. The free converter can be downloaded on CNet.
Converting a mixed track from multiple instruments to midi is not possible----A midi is a specific type of file--a certain type of sound wave (i.e. one that sounds like a piano or trombone, for example) with a set pattern of notes. You make midis by using a sheet music software such as MuseScore or Notation Composer. It is also possible to convert midis to mp3 format. However, it is NOT possible to reverse theconversion. Once a midi is converted to mp3, it loses all data specific to midis that makes the filecompatibleas a midi. Therefore, it is a one-way process, and you cannot convert any type of file to midi (midi is the "full acronym" for .mid files, by the way) as far as I know.I hope that helps and is understandable! If not, think of it as burning something: you can burn a piece of paper, but you can't freeze ash back into paper. :)(Did I also mention I'm fifteen?)