Western music is generally broken down into six periods. Each of these periods have certain characteristics which have shaped it and remained with it throughout its duration. However, lesser characteristics may change within any given period, and so you have works which fall into, say, the early Romantic period as opposed to the late Romantic.
The Medieval Period (400-1400)
Prior to about 900, nearly all the music we have any record of is a simple, one line structure called a plainchant. This was made up of one melodic line sung in unison by everybody. More complex music existed, but as it was secular and not sacred, we have very few, if any, written accounts of it.
Gradually, over the next 500 years, people began to expand on this simple structure by adding voices. At first, these voices sung a fixed interval1 above or below the original line. This was called an organum.
At some point, someone got the idea of having two different lines moving at the same time but not having a fixed interval. Usually the higher of these lines would be fairly florid, while the lower was a slower, pre-existing plainchant2.
By 1300, three and four voice compositions were being written. These works are referred to as polyphonic (many voices), to distinguish them from the monophony (single voice) of the simple plainchant.
The Renaissance (1400-1600)
By 1400 or shortly thereafter, several composers were writing polyphony in a slightly different way. Instead of using a slower bottom voice and faster upper voices, they made all voices equal in rhythmic variety. And instead of using four different chants, they used a single chant which was stated in each of the voices, upon their entrance, and the developed differently from one voice to the next. This led to a more unified sounding work, and gave rise to a number of contrapuntal (note-against-note) forms, such as the Canon (exact repetition in all the voices), the Canzon (a succession of themes, each developed and then discarded3), and the Fugue (one theme developed extensively).
Most of the development during this period was made in Italy. This is only natural as the Catholic church was the dominant force during this period, and was headquartered in Rome. Many of the best musicians wrote masses and other works for the church; nearly all of these works are in Latin, as this was the language used for services at the time. However, with the Reformation and rise of Protestantism in the latter half of the 16th Century, the nature of music had to change.
The Baroque Period (1600-1750)
One of the major changes in daily life around 1600 was the switch from the Catholic church to various Protestant religion4. The result of this change was that the language of the services switched from Latin to German. Because most people had not spoken Latin, the masses could be as ornate as the composer desired. But if the language was understandable by the majority of the people, the music should be simple enough that they could understand the words. As a result, the Catholic Latin mass was no longer needed, but new German services were. New hymns (chorales) were written to provide music for these services. These were primarily homophonic (simple chordal structure) in nature, contrasting with the polyphony that continued in instrumental and Latin works.
每一篇SAT阅读素材均有其主要观点或中心主题。典型的围绕文章主要观点的问题大多是：在这篇文章中作者的主要目的是什么?这篇文章主要涉及什么问题?这篇文章主要建议是什么?这篇文章总体上想要回答什么问题等。读完每一篇SAT阅读素材，我们都要针对SAT素材想想这几个问题。
由于SAT阅读考试的难度相对较大，所以在备考SAT阅读考试的过程中，考生需要做更多的准备，掌握一些SAT阅读技巧。大家在备考自己的SAT阅读考试的时候，可以适当的参考和借鉴一下。