interval

—intervalic, intervallic /in'teuhr val"ik/, adj.

/in"teuhr veuhl/, n.

1. an intervening period of time: an interval of 50 years.

2. a period of temporary cessation; pause: intervals between the volleys of gunfire.

3. a space between things, points, limits, etc.; interspace: an interval of ten feet between posts.

4. Math.

a. the totality of points on a line between two designated points or endpoints that may or may not be included.

b. any generalization of this to higher dimensions, as a rectangle with sides parallel to the coordinate axes.

5. the space between soldiers or units in military formation.

6. Music. the difference in pitch between two tones, as between two tones sounded simultaneously (harmonic interval) or between two tones sounded successively (melodic interval).

7. Chiefly New Eng. intervale.

8. Cards. a period in a game for placing bets.

9. Brit. an intermission, as between the acts of a play.

10. at intervals,

a. at particular periods of time; now and then: At intervals, there were formal receptions at the governor's mansion.

b. at particular places, with gaps in between: detour signs at intervals along the highway.

[1250-1300; ME intervall(e) < L intervallum interval, lit., space between two palisades. See INTER-, WALL]

Syn. 3. opening, gap, separation, gulf.

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In music, the inclusive distance between one tone and another, whether sounded successively (melodic interval) or simultaneously (harmonic interval).

In Western music, intervals are generally named according to the number of scale-steps within a given key that they embrace; thus, the ascent from C to G (C–D–E–F–G) is called a fifth because the interval embraces five scale degrees. There are four perfect intervals: prime, or unison; octave; fourth; and fifth. The other intervals (seconds, thirds, sixths, sevenths) have major and minor forms that differ in size by a half step (semitone). Both perfect and major intervals may be augmented, or enlarged by a half tone. Perfect and minor intervals may be diminished, or narrowed by a half tone.

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▪ music

 in music, the inclusive distance between one tone and another, whether sounded successively (melodic interval) or simultaneously (harmonic interval). In Western tonality, intervals are measured by their relationship to the diatonic scales in the major-minor system, by counting the lines and spaces between the given notes (always upward from the lower note).

      Simple intervals encompass one octave or less. Compound intervals are larger than the octave and are heard as expanded variants of their simple counterparts: a tenth (octave plus a third, such as C–C′–E′) is associated by the ear with a third (an interval encompassing three scale steps, such as C–E).

      Measured as described above, the scale yields four perfect intervals: prime, or unison; octave; fourth; and fifth. The other intervals (seconds, thirds, sixths, and sevenths) are major when they are built from the first degree ( tonic) of a major scale and minor when they are one semitone, or half-step, smaller (as in the third, sixth, and seventh built on the tonic of a natural minor scale).

      An interval a semitone larger than a major or perfect interval but including the same number of lines and spaces on the staff is called an augmented interval; in like manner, an interval smaller than a perfect or minor interval is called diminished. In the C major and A (natural) minor scales, the interval F–B is an augmented fourth and the interval B–F is a diminished fifth.

      When the lower pitch of a simple interval is moved up an octave to become the higher pitch, the interval is said to be inverted and takes on a different name. Thus, the third A–C and the sixth C–A are inversions (inversion) (or complements) of each other. Unison and octave; second and seventh; third and sixth; and fourth and fifth are related in this way. Major intervals become minor when inverted and vice versa; augmented intervals become diminished and vice versa; and perfect intervals remain perfect. For example, when the major second (as C–D) is inverted, the resulting seventh (as D–C) is a minor seventh; the inversion of the perfect fourth is the perfect fifth.

      In the tonal system, intervals are traditionally defined in terms of consonance and dissonance. Consonances include the perfect intervals and the major and minor thirds and sixths (imperfect consonances). Seconds, sevenths, and all augmented and diminished intervals are categorized as dissonances. The perfect fourth, a special case, is a consonant interval except when it is formed with the bass, as in two-part counterpoint, in which case it is a dissonance. Dissonant harmonic intervals may be used to create tension, and consonant harmonic intervals can resolve it.

       enharmonic intervals are identical on the keyboard but are spelled differently in notation, depending on the harmonic context in the key; the difference is important, because, for instance, the diminished seventh is a dissonant interval while its enharmonic equivalent, the major sixth, is consonant. Similarly, the distance from G to G♯ is called a chromatic (chromaticism) semitone because it is considered an alteration of the same pitch; from G to A♭ is a diatonic semitone because it represents two adjacent degrees in a diatonic scale.

Mark DeVoto

 

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