In what way is a tone cluster typically structured?

A tone cluster is characterized by having several pitches that are closely spaced together, often only a half step apart. This close proximity of notes creates a dense and dissonant sound, which is a hallmark of tone clusters. These clusters can incorporate combinations of notes that may belong to a particular scale or may even be chromatic but emphasize the effect of the aggregate sound rather than traditional harmonic structures.

When considering how tone clusters are structured, the idea of pitches varying in distance might stem from certain methods of exploring harmony, but it doesn't specifically define a tone cluster, which relies on the proximity of notes rather than their spacing. The notion of using exactly a whole step between each note would create intervals that typically do not capture the essence of a tone cluster. Predictable major or minor chord progressions are also antithetical to the concept of tone clusters, as they follow strict harmonic rules, while tone clusters thrive on dissonance and the collision of pitches.

Thus, the defining characteristic of a tone cluster is indeed that it consists of several pitches that are close together, commonly within half steps, creating a unique and impactful sonic experience.