Classical composers often aspire to imbue their music

　　Characteristics
Given the extremely broad variety of forms, styles, genres, and historical periods generally perceived as being described by the term "classical music," it is difficult to list characteristics that can be attributed to all works of that type. Vague descriptions are plentiful, such as describing classical music as anything that "lasts a long time," a statement made rather moot when one considers contemporary composers who are described as classical; or music that has certain instruments like violins, which are also found in other genres. However, there are characteristics that classical music contains that few or no other genres of music contain.
Literature
The most outstanding and particular characteristic of classical music is that the repertoire tends to be written down. Composers and performers alike are typically highly literate in understanding notation and the written quality of the music has, in addition to preserving the works, led to a high level of complexity within them.
Instrumentation

　　
The Dublin Philharmonic Orchestra performs Tchaikovsky's Fourth Symphony.
The instruments used in most classical music were largely invented before the mid-19th century (often much earlier), and codified in the 18th and 19th centuries. They consist of the instruments found in an orchestra, together with a few other solo instruments (such as the piano, harpsichord, and organ). The symphony orchestra is the most widely known medium for classical music.The orchestra includes members of the string, woodwind, brass, and percussion families.
Electric instruments such as the electric guitar appear occasionally in the classical music of the 20th and 21st centuries. Both classical and popular musicians have experimented in recent decades with electronic instruments such as the synthesizer, electric and digital techniques such as the use of sampled or computer-generated sounds, and the sounds of instruments from other cultures such as the gamelan.
None of the bass instruments existed until the Renaissance. In Medieval music, instruments are divided in two categories: loud instruments for use outdoors or in church, and quieter instruments for indoor use. The Baroque orchestra consisted of flutes, oboes, horns and violins, occasionally with trumpets and timpani. Many instruments which are associated today with popular music used to have important roles in early classical music, such as bagpipes, vihuelas, hurdy-gurdies and some woodwind instruments. On the other hand, instruments such as the acoustic guitar, which used to be associated mainly with popular music, have gained prominence in classical music through the 19th and 20th centuries.
While equal temperament became gradually accepted as the dominant musical temperament during the 19th century, different historical temperaments are often used for music from earlier periods. For instance, music of the English Renaissance is often performed in mean tone temperament. Keyboards almost all share a common layout (often called the piano keyboard).
Form
Whereas the majority of popular styles lend themselves to the song form, classical music can also take on the form of the concerto, symphony, sonata, opera, dance music, suite, étude, symphonic poem, and others.
Classical composers often aspire to imbue their music with a very complex relationship between its affective (emotional) content and the intellectual means by which it is achieved. Many of the most esteemed works of classical music make use of musical development, the process by which a musical idea or motif is repeated in different contexts or in altered form. The sonata form and fugue employ rigorous forms of musical development.
Technical execution
Along with a desire for composers to attain high technical achievement in writing their music, performers of classical music are faced with similar goals of technical mastery, as demonstrated by the proportionately high amount of schooling and private study most successful classical musicians have had when compared to "popular" genre musicians, and the large number of secondary schools, including conservatories, dedicated to the study of classical music. The only other genre in the Western world with comparable secondary education opportunities is jazz.