The term interval refers to the musical “distance” between two notes. This glossary provides specific entries for three intervals—half step, whole step, and octave—but any two notes may be related in intervallic terms. Their utility lies in their specificity: using intervallic terminology, musicians can speak precisely about how notes relate to one another.
A simple but inefficient way to determine the interval between notes is by counting the number of half steps separating them. For example, a whole step consists of two half steps (e.g., C to C-sharp plus C-sharp to D). An octave, as the term implies, comprises eight note letter names (A, B, C, D, etc.) but twelve half steps accommodated by the presence of the five “sharps” or “flats” interspersed among the eight notes.
As a basic musical term, “interval” appears regularly in music copyright infringement opinions. In the opinions of both ZZ Top v. Chrysler (1999) and Johnson v. Gordon (2005) one finds entertaining judicial disparagements of testimony offered by UCLA music faculty member Robert Walser (ZZ Top) and show-biz aficionado John Kenrick (the Johnson opinion consistently refers to him as “Mr. John”!) both of whom tinkered with the intervals of the works in question in attempting to influence the perception of musical similarities between them.