The word 'spiroid' has been applied to generalise visual representations of musical pitch or frequency-domain data that arrange the **octave intervals** (a doubling of frequency Hz value) on ** radii** of a two-dimensional circular form, thus producing a spiral line either of points (if discrete note-pitches are to be shown) or as a line representing a portion of the frequency-dominan continuum.

define spiroid:

using a polar coordinate system to show frequency-Hz values as points on a plane, where

→ 'pitch-class' corresponds **theta-angle** part of the coordinate

→ and the **radius-amplitude** part corresponds to the 'octave-level'