Which best describes a tone cluster?

• A. A consonant, wide-spaced chord built from diatonic steps.
• B. A single sustained pitch with a drone.
• C. A dissonant chord containing adjacent semitones, usually at least three notes.
• D. A melodic sequence moving by thirds.

Answer: (C)

Tone clusters are dense sonorities formed by stacking several adjacent chromatic notes so that every neighbor is a semitone apart. This close packing creates a harsh, dissonant sound because the intervals between the pitches are very small and lack traditional consonance. Typically a cluster includes three or more notes, all within a small range, which is what gives it that crowded, clashing feel.

That makes the description of a dissonant chord containing adjacent semitones, usually at least three notes, the best match. The other ideas describe different musical phenomena: a wide-spaced, consonant chord built from steps in a scale; a single sustained pitch with a drone; or a melodic sequence moving by thirds, which is about a tune's motion in time rather than multiple notes sounding together. Tone clusters are about simultaneous close-pitched notes and the dense texture they produce.