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Classical influence on later composers

Musical eras and their prevalent styles, forms and instruments seldom disappear at once; instead, features are replaced over time, until the old approach is simply felt as "old-fashioned". The Classical style did not "die" suddenly; rather, it gradually got phased out under the weight of changes. To give just one example, while it is generally stated that the Classical era stopped using the harpsichord in orchestras, this did not happen all of a sudden at the start of the Classical era in 1750. Rather, orchestras slowly stopped using the harpsichord to play basso continuo until the practice was discontinued by the end of the 1700s.

One crucial change was the shift towards harmonies centering on "flatward" keys: shifts in the subdominant direction. In the Classical style, major key was far more common than minor, chromaticism being moderated through the use of "sharpward" modulation (e.g., a piece in C major modulating to G major, D major, or A major, all of which are keys with more sharps). As well, sections in the minor mode were often used for contrast. Beginning with Mozart and Clementi, there began a creeping colonization of the subdominant region (the ii or IV chord, which in the key of C major would be the keys of d minor or F major). With Schubert, subdominant modulations flourished after being introduced in contexts in which earlier composers would have confined themselves to dominant shifts (modulations to the dominant chord, e.g., in the key of C major, modulating to G major). This introduced darker colors to music, strengthened the minor mode, and made structure harder to maintain. Beethoven contributed to this by his increasing use of the fourth as a consonance, and modal ambiguity—for example, the opening of the Symphony No. 9 in D minor.

Ludwig van Beethoven, Franz Schubert, Carl Maria von Weber, Johann Nepomuk Hummel, and John Field are among the most prominent in this generation of "Proto-Romantics", along with the young Felix Mendelssohn. Their sense of form was strongly influenced by the Classical style. While they were not yet "learned" composers (imitating rules which were codified by others), they directly responded to works by Haydn, Mozart, Clementi, and others, as they encountered them. The instrumental forces at their disposal in orchestras were also quite "Classical" in number and variety, permitting similarity with Classical works.

However, the forces destined to end the hold of the Classical style gathered strength in the works of many of the above composers, particularly Beethoven. The most commonly cited one is harmonic innovation. Also important is the increasing focus on having a continuous and rhythmically uniform accompanying figuration: Beethoven's Moonlight Sonata was the model for hundreds of later pieces—where the shifting movement of a rhythmic figure provides much of the drama and interest of the work, while a melody drifts above it. Greater knowledge of works, greater instrumental expertise, increasing variety of instruments, the growth of concert societies, and the unstoppable domination of the increasingly more powerful piano (which was given a bolder, louder tone by technological developments such as the use of steel strings, heavy cast-iron frames and sympathetically vibrating strings) all created a huge audience for sophisticated music. All of these trends contributed to the shift to the "Romantic" style.

Drawing the line between these two styles is very difficult: some sections of Mozart's later works, taken alone, are indistinguishable in harmony and orchestration from music written 80 years later—and some composers continued to write in normative Classical styles into the early 20th century. Even before Beethoven's death, composers such as Louis Spohr were self-described Romantics, incorporating, for example, more extravagant chromaticism in their works (e.g., using chromatic harmonies in a piece's chord progression). Conversely, works such as Schubert's Symphony No. 5, written during the chronological end of the Classical era and dawn of the Romantic era, exhibit a deliberately anachronistic artistic paradigm, harking back to the compositional style of several decades before.

However, Vienna's fall as the most important musical center for orchestral composition during the late 1820s, precipitated by the deaths of Beethoven and Schubert, marked the Classical style's final eclipse—and the end of its continuous organic development of one composer learning in close proximity to others. Franz Liszt and Frédéric Chopin visited Vienna when they were young, but they then moved on to other cities. Composers such as Carl Czerny, while deeply influenced by Beethoven, also searched for new ideas and new forms to contain the larger world of musical expression and performance in which they lived.

Renewed interest in the formal balance and restraint of 18th century classical music led in the early 20th century to the development of so-called Neoclassical style, which numbered Stravinsky and Prokofiev among its proponents, at least at certain times in their careers.