V. Chromaticism
Chromatic Sequences
Bryn Hughes
KEY TAKEAWAYS
- Diatonic sequences repeat musical segments and are transposed in a regular pattern within a key.
- Chromaticized diatonic sequences can include chromatic embellishments or chromatic chords, such as applied (secondary) dominants. These sequences avoid strict transposition of both interval size and quality.
- Chromatic sequences differ from diatonic sequences in that both the size and quality of the interval of transposition is maintained throughout the sequence. Diatonic sequences preserve the interval size, but not the quality, to ensure that they stay within a single key.
- Remember, with all sequences, the voice leading must be consistent within every voice. Chord voicings should match between all corresponding components.
Descending-Fifths Sequence
Consider the following example (
), often referred to as the “descending-fifths sequence.”
The sequence model, a root progression by descending fifth, is transposed down by second in each subsequent copy of the model. Because the sequence uses chords entirely from the key of G major, the root motion doesn’t match exactly throughout the sequence. For example, the root motion between the IV and viio chords is an augmented fourth, whereas the root motion between every other pair of chords is either a perfect fifth or perfect fourth. We “cheat” in the sequence in this way in order to keep the music within a single key. If the interval between successive chord roots was consistently a perfect fifth/fourth, the root progression would be as follows: G–C–F–B♭–E♭–A♭–D♭… and so on. The sequence would rather quickly bring the music outside of the key of G major, and into new chromatic territory. It would become a chromatic sequence.
Chromatic sequences differ from their diatonic counterparts in a few important ways:
- The chords that initiate the sequence model and each successive copy contain altered scale degrees.
- The chords within the pattern are of the same quality and type as those within each successive copy of that pattern.
- The sequences derive from those that divide the octave equally.
Importantly, chromatic sequences are not merely sequences that contain chromatic pitches.
shows the same descending-fifths sequence, this time with alternating secondary dominant chords. While the sequence contains chromatic chords (the secondary dominants), it is not a truly chromatic sequence because the overall trajectory of the sequence is still one that traverses the scale steps of a single key. Notice that the progression of chord roots on successive downbeats still matches the purely diatonic sequence shown in : G–F♯–E–D.
Conversely, we can create a truly chromatic sequence if we ensure that the progression of chord roots maintains a consistent pattern of intervals throughout the sequence. An easy way to do this is to make the second chord of the sequence model into a dominant-seventh chord that can be applied to the first chord of the subsequent