Also see: Outlines of Grout History of Western Music, David Papandrew
Musicology
Free Handouts
Note that human life does not lend itself well to restricted categories
and both the dates and the styles are subject to change and debate among scholars.
Historical Era
Approximate dates
Representative Composers
(Small sample)
Medieval ca. 500-1450 Hildegard von Bingen, Machaut, Landini, Léonin, Pérotin.
See: Wikipedia List
Renaissance 1450-1600 Josquin, Dufay, Palestrina.
See: Wikipedia List
Baroque
Also see: 1725-1770 Roccoco (and/or Galant) 		1600-1750 Bach, Vivaldi, Tartini, Geminiani, Handel.
See: Wikipedia List
Classical 1750-1820 Haydn, Mozart, Beethoven.**
See: Wikipedia List
Romantic
Also see: Nationalism - Grieg, Sibelius 		1820-1910 Schubert, Schumann, Chopin, Paganini, Brahms.
See: Wikipedia List
Contemporary, also referred to as 20th Century or Modern. Includes subcategories such as:
Impressionism: Debussy, Ravel
Expressionism: Schoenberg, Berg, Webern
Americana: Copland
Neo Classicism: Stravinsky, Copland
Neo Romanticism: Piston, Barber, Hanson
Experimentalism: Brown, Cage
Minimalism: Glass, Reich

Also see: Further Discussion: Contemporary Musicology

1910-present Bartók, Bernstein, Cage, Babbit, Gershwin, Varese, Messiean, Stockhausen, Takemitsu.
See: Wikipedia List

** From A History of Western Music: "Through external circumstances and the force of his own genius he transformed this heritage and became the source of much that was characteristic of the Romantic period. But he himself is neither Classic nor Romantic; he is Beethoven, and his figure towers like a colossus astride the two centuries." [Donald Jay Grout. (3rd Edition with Claude V. Palisca.) W. W. Norton & Co., Inc. New York. 1973. p. 521. Newest ed. of the Grout, 8th ed., Burkholder Grout 8th ed.