声音有四个基本属性：音高，力度，音色，时长。
按照西方音乐的框架，如果要发出乐声（暂且定义为钢琴88个键的声音），媒介大致可以分为两类，一类是人声，一类是乐器。
发出单个音符不顶用，我们需要把音符组合在一起。用书举个例子，一本书有章节，每个章节有段落，每段又有句子，而句子是词汇组合在一起的，而词又是单字组合而成的。音乐也是类似，我们可以建立这么一个类比关系。
单字 → 词 → 句子 → 段落 → 章节 → 一本书
音符(note) → 动机 (motif) → 乐句(phrase) → 乐段（period & phrase group） → 乐章(section) → 一个完整的音乐作品
所以欣赏一个古典音乐作品其实和欣赏文学作品很类似，文学体裁有小说，诗歌，戏剧，散文等等，哎那音乐也有很多不同的形式(form)，比如什么赋格啊，交响曲啊，清唱剧啊。
我们都知道好的故事要有起承转合，像奏鸣曲式中的呈现发展再现结尾组成部分，就是用类似的技巧把音乐的故事讲好。
小时候写作文，谁没用过一些套路啊，比如什么首尾呼应，细节描写。音乐作品里也有套路，最常用最基本的三个技巧是，重复(repetition)，对比(contrast)，变调(variation)，重复对比大家都应该很清楚，但是重复多了也无聊啊，那变调是在干啥呢？变调就是类似同一件事用不同的方式来说，比如肚子叫了我们可以说”我饿了“，也可以说”惊坐觉腹饥“，总归就是要让听众有点新鲜感。
我们看小说都有主线支线，而在音乐里这个就叫织体（texture）。最常见的几种比如复调(polyphonic)，主调(homophonic)，还有单调（monophonic, 我乱翻译的）。复调是啥呢？就是多条主线交织在一起，相互辉映，但并无主从之分，类似马丁大爷的小说《冰与火之歌》，多个人物，多条主线，纷繁交杂，要写好是非常难的，要不然马丁大爷也不会十几年如一日的拖稿。同理，复调音乐分析理解起来也比其他音乐作品难很多。
主调呢就是一个主线，但有多条支线暗线陪衬，像《哈利波特》系列，主线就是哈利打怪升级战胜伏地魔的故事。基本上在巴洛克时期结束之后到现在，主调音乐一直是主流。
那单调是什么呢，可以简单理解为流水账，就一个主线，什么支线啊修饰啊都没有，之所以要提到单调，就像我们小时候学习写作文都是从写流水账开始的，西方音乐最早也是从单调的织体比如格里高利圣咏开始一步步演变的。
西方音乐具体经历了哪几个时期呢，大致的划分如下：
中世纪（Middle Ages） 450-1450
文艺复兴 （Renaissance）1450-1600
巴洛克 （Baroque） 1600-1750
古典 （Classical） 1750-1820
浪漫 （Romantic） 1820-1900
20世纪初到中期 1900-1945
20世纪中期至今 1945 - now
可以看出来，音乐的进程不是孤立的而是和文学，艺术以及政治历史紧紧结合在一起。
English Version
Sound has four basic attributes: pitch, loudness, timbre, and duration.
Within the framework of Western music, to produce musical sounds (defined here as the sounds of the 88 keys of a piano), mediums can be broadly divided into two categories: the human voice and musical instruments.
Simply producing a single note is not enough; we need to combine notes together. To draw an analogy with a book: a book has chapters, each chapter has paragraphs, each paragraph has sentences, and sentences are made up of words, which in turn are composed of individual characters. Music is similar, and we can establish a comparable relationship.
Character → Word → Sentence → Paragraph → Chapter → A Book
Note → Motif → Phrase → Period & Phrase group → Movement → A Complete Musical Work
Therefore, appreciating a classical music piece is actually quite similar to appreciating a literary work. Literary genres include novels, poetry, drama, essays, and so on, and music also has many different forms, such as fugues, symphonies, operas, etc.
We all know that a good story needs to have a beginning, development, climax, and conclusion, similar to the exposition, development, recapitulation, and coda in sonata form, which are techniques used to tell the story of music.
When we were young and writing essays, who didn’t use some techniques? There are also common techniques in musical works, the most basic three are repetition, contrast, and variation. Repetition and contrast are kinda self-explanatory but what is variation? Variation is like saying the same thing in different ways, for example, when our stomach growls, we can say “I’m hungry,” or we can say “I yearn for nourishment.” The point is to keep the audience interested.
When we read novels, there are main plot and subplots, and in music, this is called texture. The most common types are polyphonic, homophonic, and monophonic.
What is polyphony? It is when multiple main lines are intertwined, reflecting each other, but without a clear hierarchy, similar to George Martin’s novel “A Song of Ice and Fire,” with multiple characters, multiple main lines, intricately interwoven, which is very difficult to write, otherwise, Martin wouldn’t have procrastinated for so many years. Therefore, polyphonic music is much more difficult to analyze and understand than other musical works.
Homophony, on the other hand, has one main line, but many subplots and undertones, like the “Harry Potter” series, where the main line is Harry’s story of leveling up and defeating Voldemort. Basically, from the end of the Baroque period to the present, homophonic music has been the mainstream.
So, what is monophony? It can be simply understood as with just one main line, without any subplots or embellishments. The reason to mention monophony is like when we were learning to write essays, we started with straightforward accounts, and Western music also evolved step by step from monophonic textures like Gregorian chant.
What periods has Western music specifically gone through? The general divisions are as follows:
Middle Ages, 450-1450
Renaissance, 1450-1600
Baroque, 1600-1750
Classical, 1750-1820
Romantic, 1820-1900
Early to Mid-20th Century, 1900-1945
Mid-20th Century to Present, 1945 - now
As can be seen, the course of music is not isolated but is closely intertwined with literature, art, economics and political history.