Abstract: Orchestra is a large instrumental ensemble band which is capable of expressing complex emotions. An orchestra mainly consists of three sections: stringed instruments, wind instruments (including brass and woodwind instruments) and percussion instruments. Each section contains many different instruments from a same family. Every single instrument has its own unique characteristics and is played in harmonious cooperation with other instruments in the orchestra. This essay explores the isomorphic expression relationship between instruments in the orchestra as well as researches the aesthetic isomorphism among the composer, conductor, performers and audience.
　　Keywords: isomorphic expression relationship, instruments, orchestra
　　? The isomorphism in each instruments section
　　Orchestra which has a powerful musical performance capability is a large instrumental ensemble group composing normally of three sections –stringed instruments section, wind instruments section (including brass and woodwind instruments) and percussion instruments section. Other instruments such as the piano and celesta may sometimes be grouped into a fourth section like a keyboard section or may just stand alone. This essay focuses on the normal three sections. Orchestra has been subdivided into several different forms by the different genres of compositions, performance venues and social functions: A normal orchestra group is often consisted of more than seventy people, in some case over a hundred. The Chamber Orchestra is a small-sized one of about fifty musicians or fewer. And the Sinfonietta which contains thirty to fifty musicians is a middle sized orchestra, mainly playing the music like the Baroque or Classical Music. A full-size orchestra (about 100 musicians) may sometimes be called a Symphony Orchestra or Philharmonic Orchestra. These modifiers do not necessarily indicate any strict difference in either the instrumental constitution or role of the orchestra, but can be useful to distinguish different ensembles based in the same city, such as the Beijing Symphony Orchestra and the Beijing Philharmonic Orchestra. Besides, there are also some other orchestra genres. For example, Light Music Band which specialized in playing soft music and Theatre Band for the opera or ballet performances[1]. Although there are different genres of orchestra, they have something in common relating to the arrangement of each instrument sections. Isomorphism is the condition of consonance and harmony. And isomorphic expression relationship is the relationship between each portion which expresses the same feeling leading to the condition of consonance and harmony. 　　? The internal isomorphic relationship in string instruments section
　　The string instruments section is often composed of two types of instruments—bowed and plucked instruments. Bowed instruments are those including violin, viola, cello and double bass etc.. While instruments like harp, organ and banjo are belong to plucked instruments. However, except for harp, other plucked instruments are rarely used in the performance. Violin section which is generally divided into two portions is one of the most important bowed instruments in the orchestra. The music played by violin is the closest sound to the human voice, and violin has a wide scale and strong performance capacity. The viola is slightly larger than violin, and the key of each string is perfect five intervals lower than that of violin separately. The timbre of viola often brings scenery of sereneness and elegance. Cello with a wide scale is about twice larger than violin. It can create muffled sound as well as a brilliant and beautiful treble. Because of these merits of cello, there are usually many solo parts for cello. As the largest and lowest-pitched instrument in the viol family, double bass may not as flexible as other instruments. But it is essential for an orchestra since it can make a stereo effect of music. The sound of harp is crisp, pure and elegant. When playing arpeggio in harp, it creates sounds that can evoke the sense of flowing water and scenic countryside. With the special timbre, harp often acted as role of harmonic accompaniment[2].
　　Although these plucked instruments are different in terms of appearance, timbre and playing method etc., they are able to cooperate well with each other in the music, reaching an isomorphism in expression.
　　? In the symphonic poem which composed by Qiming Lu in 1965, the melody of violin in the fifth section is an isomorphic expression with that of viola in the fourth section (Shown in Fig.1). Both of them express the memory of the revolution in the past hard time.[3]
　　? In the19 Page of the score of which was composed by Benjamin Britten in 1946, the cello solo section followed harmonically by a viola solo section. The lyrical sense is the result of isomorphism of cello and viola.
　　? The internal isomorphic relationship in wind instruments section
　　Wind strings including brass and woodwind instruments have a large volume in the orchestra. Although the number of musicians in wind instruments section is not dominant, they play an important role in the whole group. Each wind instrument forms an independent part and has many solo chances. Therefore, musicians in wind instruments section have to face many strict requirements such as pitch, timbre and musical quality. The wind instruments can be divided narrowly into two categories: the brass instruments (including horn, trumpet, cornet and trombone etc.) and woodwind instruments (including flute, oboe, clarinet, saxophone and bassoon etc.). Widely speaking, all the instruments that contain some type of resonator (usually a tube) can be included in wind instruments family, such as tubular bells and organ pipe[4]. The magnificent and broad sound which other instruments can hardly reach is the common feature of brass group. While woodwind instruments are usually used to play mellow music and they are also important solo instruments. 　　Wind instruments often appeared as a solo part in the orchestra, which makes their characteristic more distinguished. Interestingly, these individualized instruments can also get an isomorphism in music.
　　? At the beginning of , the melodies and sound efforts of trumpet, horn, trombone and tuba create a same sense evoking the solemn and sacred moment of the establishment of People’s Republic of China[3].
　　? In the fourth movement of , there is an expressional isomorphism between trumpet, flute, oboe and clarinet: after trumpet play the melody and repeat it, the last three instruments play the same melody. With the fast tempo and vivacious progress of eighth note and sixteenth note, these wind instruments express the excellent skills and vigorous pace of Chiwei Team[5].
　　? In the fifth movement of , flute and English horn appear continuously and work together to bring audience back to a scenery of tranquil and serene[5].
　　? The internal isomorphic relationship in percussion instruments section
　　Percussion instruments are most commonly divided into two classes: Pitched percussion instruments which produce notes with an identifiable pitch and unpitched percussion instruments which produce notes without an identifiable pitch. The percussion section of an orchestra often contains instruments such as timpani, snare drum, bass drum, cymbals, triangle and tambourine. Percussion instruments which may play not only rhythm, but also melody and harmony play a pivotal role in almost every style of music.
　　Percussion is commonly referred to as “the backbone” or “the heartbeat” of a musical ensemble, often working in close collaboration with bass instruments when present. Therefore the isomorphism often occurs based on the cooperative performance of percussion instruments and instruments in other sections.
　　? In the fourth movement of , sidedrum and sizzle cymbal play the role of accompaniment together. Although the two types of different instruments have diverse rhythm but they create an accelerated and tensed tempo.
　　? In the third movement of , the composer arranges a union of sections: string section (violin and viola), wind section (piccolo, flute, oboe and clarinet) and cymbal. 　　Fig. 14 Unison of string section in
　　Fig. 15 Union of wind section in
　　Fig 16 Repeated union of string section in
　　? The isomorphic complementarity of instruments
　　Isomorphic complementarity is the condition of consonant and harmonious among three sections (as integrations) when conveying the emotion of music, such as the isomorphic complementarity between string section and wind section. It is because of the isomorphic complementarity in the orchestra that makes the emotion fully expressed with the progress of music.
　　? The isomorphic complementarity between string and wind sections
　　String section is more suitable to express the delicate music, while the exalting melodies are usually played by wind instruments. While such two sections with different features can reach a common expression in the specific melody and become a complementary part of each other.
　　? In the eighth movement in , the scenery of celebration is conveyed by the “cross-talking” between flute, violin, clarinet, oboe and piccolo, especially the alternate melodies of flute and violin.
　　? In the fifth movement of , there is a solo part of oboe with the accompanying base of harp which plays the arpeggios. The bright and light melody of clarinet accompanied with the pure and mellow accompaniment of harp brings audiences into a deep memory of war. Although musicians play the oboe and harp in different melody, they are isomorphic complementarity of each other[5].
　　? The isomorphic complementarity between instruments sections
　　As said in paragraph of introduction of percussion instrument before, percussion instruments often acted as an accompaniment of musical instruments in the orchestra. Therefore, percussion instruments often appear with other instruments so as to be an isomorphic complementarity of other instruments.
　　In the third movement of , snare drum collaborates with string and wind instruments, showing a brilliant and brave figure of women soldiers. During that segment, string and wind instruments play the theme mainly with eighth and sixteenth tone, describing a relaxed mood. Snare drum plays the accompaniment also with eighth and sixteenth tone, while the difference is that there are more dotted rhythm in the music of snare drum and these dotted rhythm liven the music as a whole. 　　? The universal isomorphism of aesthetic experience
　　The isomorphism should be reached based on the thoughts of individuals. That is to say, the conception of emotion is created by individuals. The sounds made by strings or resonator are just objects without any emotion, and human beings, individuals with thoughts, convert the sound efforts to aesthetic experiences. Therefore, human thoughts play an essential role in the music performances and there is a universal isomorphism of aesthetic experience among individuals, and four dominant parts are the composer, conductor, performers and audiences.
　　? The aesthetic isomorphism between audience and composer
　　Professor Bo Shen from Yunnan Art University pointed it in his book that as a symbol of human life activities, musical works is not isolated music, but a sound combination of significant expression [6]. Composers choose melody including rhythm, timbre and pitch etc. with technics like harmony and polyphony to compose and audience experience the emotion of composers by listening the final arranged music. Only when audience reach the aesthetic isomorphism with composers can they fully feel the significance of music. For example, composers often use dotted rhythm and triple time to express happy mood, while audience cannot help swinging followed the music when these melodies appear. That is what we called aesthetic isomorphism between audience and composer. The Symphony No. 5 in C minor of Ludwig van Beethoven is one of the best-known compositions in classic music and one of the most frequently played symphonies. It begins by stating a distinctive four-note “short-short-short-long” motif twice. This four-note opening motif is known worldwide and be considered as the “knock of fate”. Although this piece was composed in the age far back from our own day, we can still feel the notes “knock of fate”. Shur Bart who is considered as the founder of aesthetics said that human heart is the resonator of musicians. If heart does not work, musicians would never create great works[7].
　　? The aesthetic isomorphism between conductor, performers and composer
　　Although composers write every note clearly on the score, there are some differences between each performance. Some details, such as the stroke of the bow, breath between each movement, cannot be described by writing. Conductors and performers often show the music by grasping the main direction of composer’s intent and adding their specific understanding of the work. However, it could not be a perfect performance until the conductor and performers grasp the emotion of the composer correctly. “When I was a little boy, I played the concertos of Beethoven and Mozart. No matter who you are, if you acquire the skill, you can play them”, said violinist Yehudi Menuhin when he talked to his personal experience, “but there are few musicians can express them well enough.”[8] The most challenging part of play, to many musicians, is not the skills but more about the expression. 　　Only when musical works are performed and accepted by people can they become animated. The true existence of music belongs to the acceptance. Pieces cannot work on the consciousness before they are performed[9]. From this point, the development of music needs a series of works: the initial stage of composer’s creative work, the second stage of recreations by conductor and performers, and the final stage of audience’s acceptance. Stages are interrelated and indispensable. During this process, conductor and performers passively accept the compositions of composers at first, and then they actively play the music and finally passively accepted by the audience. While for audience, they passively accept the performance from conductor and performers at first, and then accept it actively. The emotional understanding is based on the aesthetic isomorphism among the composer, conductor, performers and audience.
　　? Conclusions
　　This essay explores the isomorphic expression relationship between instruments in the orchestra from two parts: The isomorphism in each instruments section; the isomorphic complementarity of instrumental expression in music, and finally discusses the universal isomorphism of aesthetic experience. By analyzing the scores of , < Young Person's Guide to The Orchestra> and , the isomorphism is preferably described in the orchestra better. Realizing the isomorphic expression relationship can help us to understand music, especially the behavior of music appreciation. Actually the isomorphic relationship is more complex and this essay is a simple exploration. It should be realized that the music communication is a complicated and comprehensive system.
　　References
　　[1] Suijin Zhen, Jing Li, Courses of Western Music[M], Beijing, Communication University of China Press, 2005.
　　[2] Jianming Qian, The Timbre Art of Orchestra[J], Jiaxiang –Journal Xi’an Conservatory of Music, 1993, 4: 24-30.
　　[3] Jianhui Guo, Analyzes of [J], Shandong Social Sciences, 2014, 5:342-343.
　　[4] Xiaohua Wang, The World Folk Music[M], Shanghai Music Publishing House, 2008.
　　[5] Zuqiang Wu, [M], People’s Music Publishing House, 2004.
　　[6] Po Shen, Aesthetic Consciousness and Music Culture[M], Yunnan, Yunnan University Press, 2005.
　　[7] Qiansan He, Analyzes of Music by the Western Philosophers, Literati and Musicians[J], Music Research, 1980, 2: 100-119.
　　[8] Robin Daniels, Conversations with Menuhin[M], Beijing, People’s Music Publishing House, 1984
　　[9] Zofia Lissa, the New Book of Music Aesthetics theory[M], Beijing, People’s Music Publishing House, 1992