Answer:
<em>Gregorian Chant </em>One voice singing a chant melody, accompanied by one or more voices singing the same rhythm. It is monophonic.
<em>Organum </em>Non-liturgical Latin poems set to simple melodies. It is also a polyphonic work.
<em>Conductus </em>Non-liturgical compositions that often featured two singers. It is also a polyphonic work.
<em>Motet </em>A cappella, monophonic settings of liturgical texts.
I have set the 4 compositional styles chronologically.
