The chromatic scale upon which Western music is based consists of twelve pitches. Each Major or minor key uses only a subset of the total chromatic: In the case of Major, each key contains seven pitches. If a progression consists exclusively of pitches from the key, it is considered to be completely diatonic. If pitches outside the key are introduced, the music is said to become more chromatic.
The theme of the 2nd movement of Robert Schumann’s Symphony No. 3, “Rhenish,” begins with tonic and dominant harmony.
Later, a chromatic version of the theme occurs that incorporates pitches outside the key.
Chromaticism can be momentary or more sustained.
The first note of Wolfgang Amadeus Mozart’s Piano Sonata in a-minor is inflected with a chromatic grace-note—as momentary as it gets!
When the theme returns later in the movement, Mozart expands the upbeat into a complete chromatic run.
The chromaticism in this excerpt from Ludwig Van Beethoven’s Quartet in E-flat Major, Opus 74,“Harp,” is more extensive: The slow moving chromatic line leads eventually to a tonic cadence.
The moving lines in the following excerpt from Joseph Haydn’s Piano Sonata No. 62 in E-flat Major are almost entirely chromatic.
This excerpt from Ludwig Van Beethoven’s Piano Sonata in E-Major, Opus 109, has only one brief chromatic note.
Its return slightly later in another key includes more pervasive chromaticism.
Chromaticism has many functions: It can help accentuate a particular note. In Ludwig van Beethoven’s Für Elise, a chromatic note decorates the fifth scale degree.
At the refrain of the melody, Beethoven even extends the decoration.
Chromaticism can help lead more strongly to a non-tonic chord, thereby foreshadowing or recollecting important harmonic goals. This is a bit like looking at a brochure before visiting somewhere or flipping through the photo album afterwards.
The opening theme of Beethoven’s Sonata in A-Major includes a deceptive cadence strengthened by chromaticism.
Later, this momentary emphasis is expanded into a move to the key of f#-minor, the chord emphasized by the deceptive cadence. Fragments of the theme appear. The earlier chromaticism has helped to prepare this key as a target of modulation.
The second movement of Franz Schubert’s String Quintet in C opens with an expansive progression in E-Major.
The turbulent middle section is in the distantly related key of f-minor, which shares only two pitches with the original key. The shift from E to f is prepared only by a trill.
The closing passages chromatically blends the two keys. Within the return to E-Major, Schubert incorporates an allusion to f-minor. If there are any doubts about Schubert’s intentions, they are answered by the trill, which reinforces the connection.
Chromaticism can create modal mixture by borrowing chords from the opposing mode.
In the “Brindisi” (“Drinking Song”) from Giuseppe Verdi’s Otello, Iago first enjoins his comrades to drink with him in Major. Then, as he repeats the words “beva, beva” (“drink up, drink up”), he shifts to minor, concluding with a descending chromatic scale that leads to a cadence back in Major.
The opening of Ludwig van Beethoven’s Sonata in C-Major, Opus 53, “Waldstein,” begins in Major but quickly makes it way to an arrival in minor, where the fast moving rhythm stops. The music briefly pauses before resuming in Major.
At the end of the movement, Beethoven revisits the tension between Major and minor: In this excerpt, the same progression is played three times. The progressions are identical except for a single pitch borrowed from minor.
No matter how much chromaticism is present, the cadence is the final arbiter of harmonic motion: If the tonic is strongly affirmed, the music is still rooted in that key.
Compare these excerpts from Franz Schubert’s Piano Sonata in B-flat Major, D. 960. The first, while incorporating a considerable amount of chromaticism, nevertheless cadences only in one key. The second, based on the same motivic material, moves through five keys.
If the notes of the scale are considered a “family,” chromaticism is like having guests. The greater the number of guests or the longer they stay, the greater the complexity of the social dynamics. Generally, the greater the amount of chromaticism, the more disruptive it is to the stability of the key.