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Classicism

In the middle of the 18th century, Europe began to move toward a new style in architecture, literature, and the arts, generally known as Neoclassicism. This style sought to emulate the ideals of Classical antiquity, especially those of Classical Greece. Classical music used formality and emphasis on order and hierarchy and a "clearer", "cleaner" style that used clearer divisions between parts (notably a clear, single melody accompanied by chords), brighter contrasts, and "tone colors" (achieved by the use of dynamic changes and modulations to more keys). In contrast with the richly layered music of the Baroque era, Classical music moved towards simplicity rather than complexity. In addition, the typical size of orchestras began to increase, giving orchestras a more powerful sound.

The remarkable development of ideas in " natural philosophy " had already established itself in the public consciousness. In particular, Newton's physics was taken as a paradigm: structures should be well-founded in axioms and be both well-articulated and orderly. This taste for structural clarity began to affect music, which moved away from the layered polyphony of the Baroque period toward a style known as homophony, in which the melody is played over a subordinate harmony. This move meant that chords became a much more prevalent feature of music, even if they interrupted the melodic smoothness of a single part. As a result, the tonal structure of a piece of music became more audible.

The new style was also encouraged by changes in the economic order and social structure. As the 18th century progressed well, the nobility became the primary patrons of instrumental music, while public taste increasingly preferred lighter, funny comic operas. This led to changes in the way music was performed, the most crucial of which was the move to standard instrumental groups and the reduction in the importance of the continuo —the rhythmic and harmonic groundwork of a piece of music, typically played by a keyboard (harpsichord or organ) and usually accompanied by a varied group of bass instruments, including cello, double bass, bass viol, and theorbo. One way to trace the decline of the continuo and its figured chords is to examine the disappearance of the term obbligato, meaning a mandatory instrumental part in a work of chamber music. In Baroque compositions, additional instruments could be added to the continuo group according to the group or leader's preference; in Classical compositions, all parts were specifically noted, though not always notated, so the term "obbligato" became redundant. By 1800, basso continuo was practically extinct, except for the occasional use of a pipe organ continuo part in a religious Mass in the early 1800s.

Economic changes also had the effect of altering the balance of availability and quality of musicians. While in the late Baroque, a major composer would have the entire musical resources of a town to draw on, the musical forces available at an aristocratic hunting lodge or small court were smaller and more fixed in their level of ability. This was a spur to having simpler parts for ensemble musicians to play, and in the case of a resident virtuoso group, a spur to writing spectacular, idiomatic parts for certain instruments, as in the case of the Mannheim orchestra, or virtuoso solo parts for particularly skilled violinists or flutists. In addition, the appetite by audiences for a continual supply of new music carried over from the Baroque. This meant that works had to be performable with, at best, one or two rehearsals. Even after 1790, Mozart writes about "the rehearsal," with the implication that his concerts would have only one rehearsal.

Since there was a greater emphasis on a single melodic line, there was greater emphasis on notating that line for dynamics and phrasing. This contrasts with the Baroque era, when melodies were typically written with no dynamics, phrasing marks, ornaments, as it was assumed that the performer would improvise these elements on the spot. In the Classical era, it became more common for composers to indicate where they wanted performers to play ornaments such as trills or turns. The simplification of texture made such instrumental detail more important, and alit so made the use of characteristic rhythms, such as attention-getting opening fanfares, the funeral march rhythm, or the minuet genre, more important in establishing and unifying the tone of a single movement.

The Classical period also saw the gradual development of sonata form, a set of structural principles for music that reconciled the Classical preference for melodic material with harmonic development, which could be applied across musical genres. The sonata itself continued to be the principal form for solo and chamber music, while later in the Classical period, the string quartet became a prominent genre. The symphony form for orchestra was created in this period (this is popularly attributed to Joseph Haydn). The concerto grosso (a concerto for more than one musician), a very popular form in the Baroque era, began to be replaced by the solo concerto, featuring only one soloist. Composers began to place more importance on the particular soloist's ability to show off virtuoso skills, with challenging, fast scale and arpeggio runs. Nonetheless, some concerti grossi remained, the most famous of which was Mozart's Sinfonia Concertante for Violin and Viola in E-flat major.