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 wave editor called Music Editor similar to Audacity.  Again, drag the file to an empty track, select the wave object, press Ctrl+Shift+A to open the Music Editor, and Export the file as mono.  One of the more useful tools that comes with the Magix Music Editor is the "Declipping" effect to restore those files that were recorded just a little too hot.

Cheers,

Rob
cinenosin.com