This video first plays the entire piece "Fors Seulement" by Johannes Ockeghem (1410-1497), while a short overview of mensural notation is given. Then, for each voice are offered two versions: one Play Along (all voices are sounding, including the part you're reading) and one Minus One (the voice of the part you're reading has been left out, so you're on your own)! You can go directly to the chapter mark of your choice! In the Minus One you will have to figure out your own musica ficta, whereas in the Play along I've given the most obvious sharps and flats.