The use of harmony and tonality in symphonic music between 1750 and 1900 reflects a
shift from classical clarity and function to romantic expression and colour. While early
classical composers focused on diatonic harmony and simple tonal structures, later
Romantic composers embraced chromaticism, and unusual modulations. These
developments are visible through the symphonies of composers such as Stamitz,
Haydn, Beethoven and Dvořák.
In the early Classical period, harmonic language was largely diatonic and functional.
Stamitz’s Symphony in D major, Op. 3 No. 2 exemplifies this, with harmony largely
restricted to primary chords, cadential progressions, lots of pedals and a clear tonic-
dominant relationship. Modulations, usually to the dominant or relative minor, were
simple and clear, supporting the binary or early sonata forms where a double return to
the tonic was used. Even here, however, there was a developing awareness of how tonal
shifts could be used to provide contrast and drama. C.P.E. Bach, a key figure in the
Empfindsamer Stil, expanded harmonic language with unexpected modulations and
expressive dissonances. In his Symphony in E minor, the second movement includes
diminished sevenths and chromatic shifts which undermine tonal stability, showing a
more colouristic and expressive use of harmony that would influence later composers.
Haydn’s harmonic language matured over his long career. His early works, such as
Symphony No. 31 (Hornsignal), still rely on functional harmony, but he begins to explore
orchestral colour and harmonic surprise such as the recapitulation of the 1st movement
starting in a minor key. As he moved away from the Esterhazy one would expect his
harmonic creativity to flourish, however largely remained the same such as in
symphony No.88 showing how patronage may not always play a role in development
and often a composer could simply build their own harmonic sound. By Symphony No.
104, he was however using more sophisticated techniques, such as the use of a
dramatic D minor introduction leading to a bright D major first subject. Within the
second movement, Haydn explores distant keys (e.g. a surprising modulation to D♭
major, bars 102–113 in the second movement), use of interrupted cadences, and circle
of fifths sequences (e.g. bars 146–155), showing that tonal direction could be used as a
dramatic tool, not just a structural one.
Mozart retained diatonic clarity but brought in greater chromaticism, particularly in his
later symphonies. In Symphony No. 40 in G minor, the second subject modulates widely
and distantly for example to B♭ major, but chromatic inflections and harmonic
suspensions add tension beneath the lyrical surface. In Symphony No. 41 (Jupiter), the
andante second movement features Neapolitan and diminished chords, demonstrating
Mozart’s subtle blending of harmonic colour within the Classical form. He also