Converting WAV or MP3 files directly to MIDI does not always produce a good output. While a monophonic wave file can be easily converted to MIDI by a computer, polyphonic music is still impossible.
I used AmazingMIDI to convert wav to MIDI. It won't recognize mp3s so I have to convert it to WAV.
I used this song as the test music:
AmazingMIDI works by matching a sound timbre provided by the user (called Tone file) with the sounds in the input WAV file. The user can adjust the settings whether to detect dim notes or set a minimum note length to recognize.
AmazingMIDI can only output a monophonic MIDI so I used Anvil Studio's merge function (under File > Merge song) to put together all the seperate MIDI files.
This is the result:
It is totally messy and not satisfactory.
Compare it with this MIDI of the same song that I sequenced:
I therefore conclude, that it is yet impossible to convert polyphonic music to MIDI flawlessly.