Here is the Time Period page on the main site I am referring too: http://imslp.org/wiki/Browse_people_by_time_period
Update 03/31/16: Been a while since we have updated this thread, probably should post our current list here:
Ancient (before ca.800 AD)
- Ancient Chinese
- Ancient Egyptian
- Ancient Greek
- Ancient Indian
- Ancient Roman
- Ancient Mesopotamian
- Ars nova (France: Late Medieval Style)
- Ballata
- Canon ?
- Chant (Plainsong) ?
- Early Medieval
- Estampie ?
- Geisslerlieder (Germany: Late Medieval Style)
- Gregorian chant ?
- High Medieval
- Late Medieval
- Polyphony (Organum) ?
- Manneristic (Ars subtilior: Late Medieval Style)
- Motet ?
- Madrigal (Trecento)* ?
- Saltarello*
- Trecento (Italy: Late Medieval Style)
- Early Renaissance
- Late Renaissance
- Madrigal (Trecento)* ?
- Saltarello*
- Early Baroque
- High Baroque
- Rococo (Galante)
- Empfindsamer Stil
- Rococo / Galante
- Empfindsamer Stil
- High Classical
- Late Classical
Romantic (1815-1920)
- Early Romantic
- Late Romantic
- Nationalistic*
- Historic*
- Post-Romantic
- Impressionistic
- Impressionistic
- Primitivistic
- Expressionistic
- Polytonalistic
- Atonal
- Serialistic
- Eclectic (Polystylistic)
- Modalistic
- Jazz*
- Historic*
- Nationalistic*
- Aleatoric
- Minimalism
- Aleatoric
- Minimalistic
- Jazz*
- Historic*
- Nationalistic*
- Eclectic (Polystylistic)
- Postmodern
- Traditional (folk music)
- African
- Americas (Western Hemisphere)
- Asian
- Australian
- European
- Polynesian
- Historicism (19th century forward)
- Pseudo-Ancient
- Pseudo-Medieval
- Pseudo-Renaissance
- Pseudo-Baroque
- Pseudo-Classical
- Pseudo-Romantic
- Jazz (20th century forward)
- Ragtime
- Stride
- Big Band
- Hot Jazz
- Cool Jazz
- Free Jazz
- Non-Western Classical
- Arabic
- Chinese
- Indian
- Indonesian
- Persian