Converting an audio file (WAV, MP3, WMA) to MIDI (Musical Instrument Digital Interface) is fairly simple to do and requires the use of a third-party software. There is no native Windows software that can do this conversion. There are some viable solutions that allow the user to choose from a variety of audio input file types and still successfully output them to MIDI.
Download and install audio editing/recording software. Some of the most popular choices for this application are Adobe Audition, Sony Soundforge and Adobe Soundbooth. All of the aforementioned software packages can be downloaded for free. All of these programs follow the same process for converting to MIDI files.
Open the audio software. Click "File", "Open" and navigate to the directory where the source audio file that will be converted is stored. Double-click on that file to import it into the program. The audio file will now be visible in the track window.
Save the file as MIDI. Click "File", "Save As." A save window will appear. Change the "File Type" to "MIDI". Enter in a "File Name" for the new MIDI track. Use the Explorer window and navigate to a directory where the file will be saved. Click "Save". The program will automatically begin converting the audio file (no matter what source format) into MIDI. This process may take several minutes. When it is done, exit the program.
Navigate to the newly outputted file and double-click it. The file should now play in MIDI file format.