Polyphonic Era
During the Polyphonic Era (1200-1650), most music consisted of the simultaneous flow of several different melodies, all independent and equally important. Usually made of four or five different choral parts, the music was originally for unaccompanied voices and was used mostly in the mass and motet of church music and the madrigal in secular music.
Gothic Period (1200-1550)
First forms of polyphonic music are developed known as Ars Antiqua - Ancient Art.
Ars Nova (14th Century)
New techniques of rhythm and melody brought more feeling to the music, paving the way for the first important polyphonic music schools. Ars Nova means New Art.
Important Polyphonic Schools (15th-16th century)
Netherland (Flemish) School: Guillaume Dufay (1400-1474), Josquin des Prez (c. 1450-1521), and Orlande de Lassus (1532-1594)
Venetian School: Adrian Willaert (c. 1488-1562), and Giovanni Gabrieli (c. 1557-c.1612)
Roman School: Giovanni Pierluigi da Palestrina (c. 1525-1594), and Tomás Luis de Victoria (c. 1548-1611)
Secular Polyphonic Music (16th Century)
Claudio Monteverdi (1567-1643) William Byrd (1543-1623) Thomas Morley (1557-1603) Orlando Gibbons (1583-1625)
Baroque Period
Forms become more elaborate, attention paid to dramatic effect, choruses combined with arias, duets and quartets with choral music accompanied by instruments. New church forms developed such as the oratorio, the passion, and the cantata. - Giacomo Carissimi (1605-1674) - J. S. Bach (1685-1750) - Heinrich Schütz (1585-1672) - G. F. Handel (1685-1759)
Sources
The Home Book of Musical Knowledge By David Ewen