Definition
A cluster is a chord made of adjacent notes a second apart (major or minor). Unlike chords built in thirds, it has no clear root: it is a block of sound whose perception depends on register, timbre, and dynamics.
Types
| Type | Example | Notes |
|---|---|---|
| Diatonic (white keys) | C D E F G | modal color, “pandiatonic” |
| Pentatonic (black keys) | C# D# F# G# A# | soft, no semitones |
| Chromatic | C C# D D# E | maximum density, tension |
| “Open” cluster (voicing in spread seconds) | C D … G A in different registers | jazz and modern pop |
History
- Henry Cowell (1897–1965) coined the term tone cluster and played it on the piano with forearms and palms: The Tides of Manaunaun (c. 1917).
- Charles Ives: in the Concord Sonata he prescribes a strip of wood to press down a cluster.
- Béla Bartók: clusters in the Piano Sonata and in Mikrokosmos.
- Krzysztof Penderecki: Threnody to the Victims of Hiroshima (1960) for 52 strings, with quarter-tone clusters that widen and narrow.
- György Ligeti: Atmosphères (1961), micropolyphony: dozens of lines in a slowly moving cluster (used by Kubrick in 2001: A Space Odyssey).
Acoustics: why register matters
Two notes a semitone apart produce beats equal to the difference in frequency:
- C3 (130.8 Hz) and C#3 (138.6 Hz): about 7.8 beats per second, a rough and muddy sound.
- C5 (523.3 Hz) and C#5 (554.4 Hz): about 31 beats per second, perceived as “shimmer” rather than roughness.
That is why close clusters are written in the middle-high register; below C3 they become noise. It is the same logic as the “low interval limits” of arrangers.
Clusters in jazz and pop
- Voicings with seconds: Cmaj9 played B – C – D – E – G (inner seconds) gives a modern color (Bill Evans, Keith Jarrett).
- Sus2 and add9 in pop: C – D – G (sus2) and the “second” between the 9 and the 3 (D – E) in Cadd9 are “tamed” clusters.
- Ambient pads: slow diatonic clusters (5–7 notes) with a 1–3 s attack and long reverb.
Clusters in film and sound design
- Strings: a chromatic cluster growing from pp to fff = terror (horror, thriller).
- Low brass: a cluster of major seconds in fortissimo = menace.
- Choirs: vocal clusters (aleatoric or written) for supernatural scenes.
How to write it (production tips)
- Distribute the notes among several instruments or tracks (each with its own note): it sounds richer and more controllable.
- Automate the volume of the individual notes to make the cluster “breathe.”
- Use an EQ to avoid buildup at 200–500 Hz; apply an HPF on low clusters.
- A chorus or a slight detune increases the perceived density.
Producer exercise
- Create 5 string tracks (or 5 instances of a pad) with the notes C4 – D4 – E4 – F4 – G4.
- Bring the notes in one at a time, one per bar (a crescendo of density) at 70 BPM.
- At the fifth bar, resolve to an open C major chord (C3 G3 E4): the effect is of “mist lifting.”
Related topics
Quartal harmony, pandiatonicism, the harmonic series, harmony for film, voicing.