Because of the dominance of the Catholic church during this time period, there was a heavy emphasis on religous music.  The Gregorian Chant was the starting form of music for this time period.  It consisted of a monophonic style without any harmonies.  The melodies were free of tempo and were dictated based on the Latin texts on which they were based.  As time progressed towards the end of the Middle Ages, some developments of polyphonic music started to come about, with some compositions successfully integrating two to five different voices together, but not done nearly as smoothly as during the Renaissance.