Hildegard of Bingen

Hildegard of Bingen was one of the most accomplished people from the Middle Ages.  She wrote books on medicine, philosophy, science and composed the music and words for a medieval type of music called monophony.  Monophony is a single line of music that is often accompanied by others who 'join in' instead of doing something different.  If you are not used to listening to it, it helps to focus on the small differences you can hear.  

Questions:

Is there a difference between the start, middle and end of a piece of monophony?

Hard:

How is monophony different from polyphony, and, how is it similar?