Selected Bibliography Architecture - Form Space and Order | Page 381

D ATU M

Excerpt from Gavotte I, Sixth Cello Suite, by Johann Sebastian Bach
(1685–1750). Transcribed for classical guitar by Jerry Snyder.

A datum refers to a line, plane, or volume of reference to which other elements
in a composition can relate. It organizes a random pattern of elements through
its regularity, continuity, and constant presence. For example, the lines of a
musical staff serve as a datum in providing the visual basis for reading notes
and the relative pitches of their tones. The regularity of their spacing and their
continuity organizes, clarifies, and accentuates the differences between the
series of notes in a musical composition.
A preceding section illustrated the ability of an axis to organize a series
of elements along its length. In effect, the axis was serving as a datum.
A datum, however, need not be a straight line. It can also be planar or
volumetric in form.
To be an effective ordering device, a linear datum must have sufficient visual
continuity to cut through or bypass all of the elements being organized. If
planar or volumetric in form, a datum must have sufficient size, closure, and
regularity to be seen as a figure that can embrace or gather together the
elements being organized within its field.

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