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.
You can convert MIDI files to scores using music notation software like Finale or Sibelius. These programs can import MIDI files and display them as sheet music that you can edit and print.
FL Studio can import MIDI files and export WAV, MP3, OGG and MIDI files.
To convert MIDI files to ABC format for use in Starbound, you can use a software program or online converter specifically designed for this purpose. These tools will allow you to easily convert the MIDI files into the ABC format that is compatible with Starbound.
Use google and search for midi files or instrumental mp3's.
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.
You can turn MIDI files into sheet music by using a music notation software program that supports MIDI file import. These programs can convert the MIDI data into notation that can be printed as sheet music.
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.
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.
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.