The Classical Style
In the middle of the 18th century, Europe began to move to a new style in the arts, architecture and literature. While still tightly linked to the court culture and absolutism, with its formality and emphasis on order and hierarchy, the new style was also a cleaner style, one that favored clearer divisions between parts, brighter contrasts and colors, and simplicity over complexity. The ideas of "natural philosophy", which had established itself in the public consciousness with Newton's physics were taken as an example: structures should be axiomatic, articulated and orderly. This taste for cleanliness worked its way into the world of music as well, moving away from the layered polyphony of the Baroque period, and towards a style where a melody over a subordinate harmony — called homophony — was preferred. This meant that playing of chords, in unison, became a much more prevalent feature of music, and this in turn made the tonal structure of works more audible.

The new style was also pushed forward by changes in economics and social structure. As the 18th century progressed, the nobility more and more became the primary patrons of instrumental music, and there was a rise in the public taste for comic opera. 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 harmonic fill beneath the music played by several instruments. One way to trace this decline of the continuo and its figured chords is to see the decline of the term "obbligato", meaning a mandatory, instrumental part in a work of chamber music. In the Baroque world, additional instruments could be added in as continuo; in the classical world, all parts were noted, though not always notated, so the word "obbligato" ceased to have any meaning. By 1800, the term was virtually extinct, as was the practice of conducting a work from the harpsichord.

This change in the economic situation altered 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 forces available at a hunting lodge were smaller, and more fixed in their level of ability. This was a spur to having primarily simple parts 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. In addition, the taste for a continual supply of new music, carried over from the Baroque, meant that works had to be performable with, at best, one rehearsal. Indeed, well into the 1790's Mozart writes about "the rehearsal", to imply that his concerts would have only one.

Since polyphonic texture was no longer the focus of music, but rather a single melodic line, there was greater emphasis on notating the music for dynamics and phrases. The simplification of texture made instrumental detail more important, and also made the use of characteristic rhythms, such as attention-getting opening fanfares, the funeral march rhythm, or the minuet, more important in establishing and unifying the tone of a single movement.

This lead to the classical style's gradual breaking with the Baroque habit of making each movement of music devoted to a single "affect" or emotion. Instead, it became the style to employ contrasts between different emotional sections, by contrasting major and minor, strident rhythmic themes with longer, more song-like themes and making movement between different harmonic areas the principal means of creating dramatic contrast and unity. Moments of transition became more and more important, as moments of surprise and delight. Consequently composers and musicians began to pay more attention to them, making their arrival more distinct, and making the signs that pointed to them, on one hand, more audible, and on the other hand, more the subject of "play" — that is, composers more and more created false expectations, only to have the music skitter off in a different direction.