http://www.sesk.org/Aesthetics/Music/Baroque.htm
http://classicalmusic.about.com/od/classicalmusic101/a/intro072104.htm

Music evolves just like anything else in life. There are various forms of jazz, rock and even folk music that changes ofer the passage of time mostly because the people who compose music flavor music with their own personalities and inventions. Needs an purposes will also contribute to change. Composers are basket weavers and eventhough music appears to be different, it is woven and entertwined together in a way that binds the various styles together. I hear similarities in all styles of music.