Two differences between Renaissance and modern music are in notation (writing music down).
The primary basic note value was larger than the modern value being the equivalent of modern whole note (beats equaling a full measure whether 2, 3, 4 etc). As a result of this larger note value, music could be more drawn out and less rapidly moving than modern music can be.
Paper came to replace vellum leading to changes in notation, which was done without barlines. On vellum, all values were blacked in, but on the weaker paper, "white mensural notation" developed in which notes were left open, not blacked in. This differs from modern notation in that openness or blacking of the note head help to indicate note value along with stems and stem flags.