When you listen to gregorian chant/plain chant such as”ave, rex

When you listen to Gregorian chant/plain chant such as”Ave, Rex noster, fili David” (link below), do you feel that It “stands alone,” or do you feel that it could use harmony, more regular rhythm, or even musical instruments to be more effective? Why?

 

500-750 Words

 

Link: http://www.wwnorton.com/college/music/enj9/shared/jukebox/medieval.swf

 

or

 

http://redmp3.cc/903443/capella-antiqua-munchen-ave-rex-noster-fili-david-antiphon.html