See also Music genres under entertainment.
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Prior to the Classical Period, polyphonic music ran together in two or more voices, using strands of melodies running along together. With the onset of the Classical Period, focus shifted to a single melody with harmonic accompaniment. Homophonic, or unisonic, music was simple, with accompaniments often consisting of broken chords that were played as single notes.

the Baroque period (ca.1600 to 1750) saw composers beginning to rebel against the styles that were prevalent during the High Renaissance.
Johann Sebastian Bach , George Frideric Handel, Antonio Vivaldi.

Vivaldi (1678 - 1741) begins the Classical Period and is sometimes even thought of as composing during a transitional time on the heels of the Baroque Period as it led into the Classical.
In western music the classical period lasted from about 1750 to 1800 and included: Mozart (1756-1791), Haydn (1732 - 1809) and Beethoven (1770-1827) who bridged the Classical and Romantic periods.
A slight bending of the "rules" near the end of the Classical Period would open the door to the more impressionistic and emotional style of the Romantic Period.

The term neoclassical in Western music refers to twentieth-century pieces that were strongly influenced by eighteenth century ideals. Links:
Classical Music and Music of the Classical Era
Classical Music at: Yahoo, Google, wikipedia
Genres

Classical Forms

Romantic:
The term Romantic covers most of the music (and art and literature) of Western civilization from the nineteenth century (the 1800's). But there has been plenty of music written in the Romantic style in the twentieth century (including many popular movie scores), and music isn't considered Romantic just because it was written in the nineteenth century.

The Romantic era produced many more composers whose names and music are still familiar and popular today: Brahms, Tchaikovsky, Schumann, Schubert, Chopin, and Wagner are perhaps the most well-known, but there are plenty of others who may also be familiar, including Strauss, Verdi, Liszt, Mendelssohn, Puccini, and Mahler. Ludwig van Beethoven.

Popular - Folk:
Lyric Intrepretations

Rock:
Music genres under entertainment
More rock

Links:
Frequency and Pitch
musictheory.net
Symphony No. 5 (Beethoven)
My Classical Selection
Music History 102
The Music of the Romantic Era
Violin Care
Violin Tuning
Violin Fingering
Ukulele
Stringed Instruments