The terms chord and harmony refer to music’s vertical dimension: They are a way of describing music that is being played at one time.
A sequence of harmonic changes is called a harmonic or chord progression. A harmonic progression may be expressed in a variety of ways. Most simply, it can be presented as series of "block" chords. Here, melodic interest is reduced; the focus is on the chord changes.
More elaborately, it can be presented as figuration, for instance on the piano: Each chord is presented as a “cascade” or “swirl” rather than as a “block.”
A chord progression may accompany a melody. In this excerpt from Frederic Chopin’s Piano Concerto No. 1, the piano’s melody is supported by harmony in the orchestra and the pianist’s lower register.
In this excerpt from Antonin Dvorak’s Symphony No. 9, “From the New World,” the brass melody is punctuated by powerful chords.
In its most intricate form, a harmonic progression may be created by the super-position of individual lines. The terms counterpoint and polyphony refer to music made up of multiple voices or lines moving independently. In Western Common Practice music, there is a union of harmony and counterpoint: Polyphony produces recognizable harmonic progressions.
Johann Pachelbel’s Canon in D opens with the following harmonic progression in block chords.
Pachelbel then invents melodic lines that grow out of this progression. In this excerpt, a faster moving line is superimposed against slower moving ones.
Voicing refers to how a harmony is distributed among the various instruments or voices. Changes in voicing allow a harmonic progression to be re-expressed in new ways.
This theme from Franz Schubert’s Cello Quintet in C is first played by the lower strings, with the accompaniment above.
The theme is repeated a short time later but with the voices flipped: This time, the melody is in the upper strings and the accompaniment below.
In Debussy’s Reverie, the main melody is first harmonized by an accompaniment by that lies beneath.
Later, the voicing is changed: Now the melody is in the middle, with the accompaniment on either side.
Voice-leading refers to how individual lines move within a chord sequence. The same progression can be voice-led in many different ways. The Scherzo of Antonin Dvorak’s Symphony No. 7 opens with this passage.
The progression is brought back later with more elaborate voice-leading.
The term texture is a way of describing how multiple factors can influence the expression of harmony: Instrumentation, voicing, voice-leading, register and rhythm all can contribute to changes in texture. When this theme is first presented in Ludwig van Beethoven’s Symphony No. 8, the upper strings and winds share the theme.
When the melody returns later, the melody is now in the lower strings. Not only that, the orchestration is different: The winds are silent; and the upper strings have added a new element - repeated notes.
In Maurice Ravel’s Bolero, the same melody and harmonic progression are repeatedly cycled in a giant loop: Interest is sustained by changes in the orchestral texture.
Thanks to all of this flexibility, the same progression can be repeated with constant novelty. For instance, in a classical Theme and Variations, the harmonic progression of the theme is presented over and over but never the same way twice.
The following excerpts enable you to compare a fragment of the theme from the Gavotte of Igor Stravinsky’s Pulcinella Suite with one of its variations: The underlying harmonic progression is the same but Stravinsky varies the orchestration and accompaniment.
The following three variations from Beethoven’s Eroica Variations for piano all share the same harmonic progression. Can you tell you which variation stretches out one of the harmonies?
The alphabet can be represented by a variety of fonts: Yet, though type-faces may vary considerably, they still represent the same letters. Similarly, thanks to variations in voicing, voice-leading and texture, harmony can be re-expressed a virtually limitless number of ways.