Haydn, having worked for over a decade as the music director for a prince, had far more scope for composing than most, and also the ability to shape the forces that would play his music. This opportunity was not wasted, as Haydn, beginning quite early on his career, restlessly sought to press the technique of building ideas in music forward. His next important breakthrough was in the Opus 33 string quartets (1781), where individual parts changed from melody to harmony and back again, and worked their way between dramatic moments of transition, and climactic sections where music flowed smoothly and seemingly without interuption. He would then take this integrated style and begin applying it to orchestral and vocal music.

Haydn's gift to music was a way of composing, a way of structuring works, which was, at once, within the new style, and rooted in principles of the old style which he drew primarily from CPE Bach. It would, however, be a younger contemporary, Wolfgang Amadeus Mozart who would bring his genius to Haydn's ideas, and apply them to two of the major genres of the day: opera, and the virtuoso concerto. Whereas Haydn spent much of his working life as a court composer, Mozart wanted public success in the concert life of cities. This meant opera, and it meant performing as a virtuoso. Haydn was neither a virtuoso at the international touring level, nor was he seeking to create operatic works that could play for many nights in front of a large audience - Mozart wanted both. Moreover, Mozart also had a taste for more chromatic chords, and greater contrasts in harmonic language, a greater love for creating a welter of melodies in a single work and a more Italiante sensibility towards music as a whole. He found, in Haydn's music, and in a study of the polyphony of Bach, the means to discipline his gifts.

Mozart rapidly came to Haydn's attention, who hailed the new composer, studied his works, and considered the younger man his only true peer in music. Their letters to each other are filled with the kind of asides that only two people working at a higher plane than their contemporaries, can share. From Mozart, Haydn found a greater range of instrumentation, dramatic effect and melodic resource - the learning relationship moved in two directions.

The arrival in Vienna by Mozart in 1780 marked the acceleration of the development of the classical style, here, Mozart absorbed the fusion of Italianate brilliance and Germanic cohesiveness which had been brewing for the previous 20 years. His own taste for brilliances, rhythmically complex melodies and figures, long cantilena melodies, and virtuoso flourishes was merged with an appreciation for formal coherence and internal connectedness. Strangely enough, it is at this point that war and inflation halted a trend to larger and larger orchestras and forced the disbanding or reduction of many theatre orchestras. This pressed the classical style inwards: towards seeking greater ensemble and technical challenge. For example, scattering the melody across woodwinds, or using thirds to create a melody between them. This process placed a premium on chamber music for more public performance, giving a further boost to the string quartet and other small ensemble groupings.

It was during this decade that public taste began, increasingly, to recognize that Haydn and Mozart had reached a higher standard of composition. When Mozart arrived at age 25, the dominant styles of Vienna were recognizably connected to the emergence of the early classical style in the 1750's. By the end of the decade, changes in performance practice, relative standing of instrumental and vocal music, technical demands on musicians and stylistic unity had become established in the composers who imitated Mozart and Haydn. During this decade Mozart would compose his most famous operas, his six late symphonies which would help redefine the genre, and a string of piano concerti which are still among the pinnacle works of the form.

One composer who was influential in spreading the more serious style which Mozart and Haydn had formed is Muzio Clementi, a gifted virtuoso pianist who dueled Mozart to a draw before the emperor in playing compositions. His own sonatas for the piano circulated widely, and he became the most successful composer in London during this decade. The stage was set for a generation of composers, having absorbed the lessons of the new style earlier, and having clear examples to aim at, who would take the classical style in new directions. Also in London at this time was Johann Ladislaus Dussek, who, like Clementi, encouraged piano makers to extend their instruments and made full use of the possibilities. The importance of London in the classical period is often overlooked - but it served as the home to the Broadwood's factory for piano manufacturing, and as the home base for composers who, while less famous than the "Vienna School" would have a decisive influence on what came later, and were composers of a number of fine works in their own right. London's taste for virtuosity may well have encouraged the complex passage work and extended statements of tonic and dominant.