1. Violin: Violin is one of the most popular stringed instruments, which occupies a very important position in instrumental music, is the pillar of modern symphony orchestra, and is also a solo instrument with difficult playing skills. Together with piano and classical guitar, it is called the three major music festivals in the world. Violin is one of the most expressive instruments, and its playing skills are extremely rich. Composers often use it to trigger the tone of their works. Violins are divided into the first violin and the second violin in the symphony orchestra. The first violin is often the main theme, and the second violin is the harmony accompaniment of the main part of music. In addition, the violin is often used for chamber music and solo in sketches.

2.Viola Viola: Viola is only one-seventh larger than violin, with almost the same shape, and is also widely used in orchestral music, symphony and chamber music (especially string quartets). Viola usually plays the role of alto, accompanying and setting off the main theme, and is rarely used for solo. However, it occasionally appears as a solo instrument. For example, in Berlioz's symphony Harold in Italy, viola solo accounts for a considerable proportion. Viola has a unique sound quality, similar to nasal intonation, which is very suitable for expressing deep and mysterious emotional appeal.

3. Cello: The history of cello can be traced back to the end of 16. This is a musical instrument developed in15th century, and it is called "double bass" or "double violin". Cello is famous for its warm and rich timbre and is one of the most common instruments in symphony orchestras. Suitable for all kinds of roles: sometimes join the bass camp, make a heavy sigh in a low voice, and sometimes play the role of rhythm backbone with two strings in the middle. The most brilliant moment of the cello is the mission entrusted to it by the composer to express the melody like a song. The wonderful melody played by the whole cello group is enough to dwarf any other instrument in the symphony orchestra.

4. Double bass: Double bass, also known as double cello, double bass and double bass, is the largest bowstring instrument with the lowest pronunciation in the violin family. The double bass is the lowest voice in orchestras and symphony orchestras, which plays an accompaniment role and is rarely used for solo, but its strong bass is undoubtedly the embodiment of the powerful power in multi-part music. Beethoven often used it to play important melodies in symphony orchestras. For example, he used the double bass recitation at the beginning of the fourth movement of the Ninth Symphony, which strongly denied the theme motivation of the first three movements. Also, in his "Animal Carnival", Saint-Sang vividly padded out a heavy and solemn elephant image with a double bass.