Open the software and select "File" from the top of the screen, then "Open." Select a MIDI file from the list of options.
Scroll down to the "Mixer" section of the screen, at the bottom.
Click the "Monitor" radio button, which is located in the mixer under each track. Click the "In" button, located under the "Monitor" section of the mixer, for each MIDI track.
Scroll up to the "Transport" area at the top of the screen and press the "Play" button. Monitor all of the MIDI tracks while the song is playing.
Save the MIDI file by selecting "File" from the top of the screen, then "Save."