Good stuff! The sound editor used in the video is called Audacity. Actually, Music Maker can also convert a stereo file to mono itself. To convert a stereo file to mono, drag the file to an empty track in the "arranger" area, "solo" only that track, select file/export/audio as wave (or press Alt+W), select the "mono" option and save the file. Alternatively, Music Maker also has a built-in