Consider the opening of Wagner's Tristan und Isolde. That famous chord—the one that supposedly launched modern music—contains a note that doesn't belong to any conventional key. It hangs in the air, unresolved, pulling the listener forward with almost physical force. This is chromaticism at its most radical: a single foreign pitch that transforms everything around it.

But chromaticism isn't always so revolutionary. Long before Wagner unsettled nineteenth-century audiences, composers from Bach to Mozart were threading chromatic notes through their harmonies with surgical precision. These colorful additions—notes borrowed from outside the prevailing key—served as the musical equivalent of shading in a pencil drawing, adding depth and dimension to the diatonic framework.

Understanding how chromaticism works reveals something essential about tonal music's expressive power. The diatonic scale gives us stability and home. Chromatic notes give us longing, surprise, and the pleasure of return. Together, they create the emotional vocabulary that Western music has developed over centuries.

The simplest form of chromaticism involves filling in the gaps. In a diatonic scale, whole steps create natural melodic distances—C to D, F to G. But what happens when a composer slides a C-sharp between C and D? The effect is subtle but unmistakable: smoother motion, a slight intensification of forward movement.

These chromatic passing tones appear everywhere in common-practice music. In a Bach chorale, you might find the bass line stepping C–C#–D rather than leaping directly. The chromatic note doesn't change the harmony—it simply decorates the connection between two stable pitches. Heinrich Schenker, the influential theorist, called such notes durchgehende: they pass through without disturbing the deeper harmonic structure.

What makes chromatic passing tones effective is their clear subordination to diatonic goals. The C-sharp exists because of the D that follows it. Our ear understands it as a temporary inflection, not a new tonal center. This is chromaticism as ornament—adding richness without threatening the underlying framework.

Yet even this modest technique carries expressive weight. Compare a melody that moves by whole steps to one that includes chromatic inflections. The chromatically altered version sounds more intense, more urgent. Composers exploit this effect constantly. Mozart's slow movements often feature chromatic passing tones at moments of heightened emotion, as if the melody itself were straining against its constraints.

Takeaway

Chromatic passing tones teach us that the path between two points matters as much as the destination—small inflections can transform the character of musical motion without changing its fundamental direction.

Every scale degree in a key has the potential to become a temporary tonic. When composers exploit this potential through secondary dominants, they create momentary gravitational pulls toward notes other than the home pitch. The technique is elegant: borrow the dominant chord of your target note, and suddenly that note feels like a destination.

In the key of C major, consider the chord progression C–A7–D minor–G–C. That A7 chord doesn't belong to C major—it contains a C-sharp. But our ear recognizes it instantly as the dominant of D, and when D minor arrives, it feels like a small resolution. The technical term is tonicization: D minor briefly acts as a local tonic before the music continues its journey home.

This technique vastly expands harmonic color without sacrificing tonal coherence. Bach's chorales are filled with secondary dominants, sometimes several in a single phrase. Each one creates a tiny moment of tension and release, enriching the harmonic rhythm while the larger progression remains firmly anchored. The music visits other key areas without moving there.

The analytical insight from Schenkerian theory proves useful here. Secondary dominants create surface-level chromaticism while the background structure—the fundamental harmonic motion—remains diatonic. The borrowed chords are understood as elaborations, intensifications of more basic progressions. This hierarchical thinking explains why heavily chromatic passages can still sound coherent: beneath the colored surface, familiar patterns persist.

Takeaway

Secondary dominants reveal that tonal music operates on multiple structural levels simultaneously—surface chromaticism creates richness while deeper diatonic frameworks maintain coherence and direction.

Sequences—patterns that repeat at different pitch levels—provide one of music's most satisfying formal devices. When those patterns involve chromatic harmony, they become vehicles for traversing vast tonal distances while maintaining a sense of logic and inevitability.

Consider a sequence that descends by half steps: a dominant seventh chord moves down chromatically, each iteration a semitone lower than the last. Individually, these chords have no clear relationship. But the pattern itself creates coherence. Our ear follows the regularity of the sequence rather than parsing each chord's function. Composers from Vivaldi to Brahms exploited this principle to move through remote harmonic territories without losing their listeners.

The chromatic sequence often appears at moments of harmonic adventure in sonata forms and concertos. When a composer needs to travel from one key area to another distant one, a well-crafted sequence provides the bridge. The chromaticism is systematic rather than arbitrary—each step follows logically from the last, even when the destination would be impossible to reach through conventional diatonic means.

What makes these passages work analytically is their combination of local unpredictability with global coherence. Any single chord in a chromatic sequence might be ambiguous; the pattern as a whole is crystal clear. This paradox—using chromaticism to create clarity—demonstrates the sophisticated logic underlying tonal music's apparent spontaneity.

Takeaway

Chromatic sequences demonstrate that coherence in music can emerge from pattern and process rather than harmonic function—systematic movement creates its own compelling logic.

Chromaticism transforms the seven-note diatonic scale into a twelve-note palette of infinite shadings. From the subtle smoothness of passing tones to the gravitational pull of secondary dominants to the systematic journeys of chromatic sequences, these techniques reveal tonal music as a flexible language capable of expressing far more than its basic materials might suggest.

What unites all chromatic practice is the relationship between foreign notes and their diatonic context. The power of chromaticism depends on having a home to depart from and return to. Without the stability of the underlying key, those borrowed pitches would lose their expressive charge.

Learning to follow chromatic voice-leading means hearing music as composers conceived it: not as a succession of isolated chords, but as a living fabric of melodic connections where every note earns its place through relationship to what surrounds it.