Home > Interval (music)
In music theory, an interval is the difference (a ratio or logarithmic measure) in pitch between two notes and often refers to those two notes themselves (otherwise known as a dyad). An interval class is measured by the shortest distance possible between its two pitch classes.Intervals may be labelled according their pitch ratios, as is commonly used in just intonation. Intervals may also be labelled according to their diatonic functionality, as is commonly done for tonal music, and according to the number of notes they span in a diatonic scale. The interval of a note from its tonic is its scale degree, thus the fifth degree of a scale is a fifth from its tonic. For atonal music, such as that written using the twelve tone technique or serialismSerialism is a rigorous system of composing music in which various elements of the piece are ordered according to a pre-determined ordered set or sets, and variations on them. The elements thus controlled may be the pitch of the notes, their length, their, integer notation is often used, such as in musical set theoryMusical set theory is a post-tonal method of analysis and composition which is based on explaining and proving musical phenomena, taken as "sets" and subsets, using mathematical rules and notation. Mathematical set theory and musical set theory Although m. Finally, it is also possible to label intervals using the logarithmic measure of centThe cent is a unit in a logarithmic scale of relative pitch or intervals. 1200 cents are equal to one octave, and an equally tempered semitone is equal to 100 cents. The formula to determine the value in cents between two notes with frequencies a and b iss, as is used to compare other intervals with those of twelve tone equal temperamentEqual temperament is a scheme of musical tuning in which the octave is divided into a series of equal steps (equal frequency ratios). The best known example of such a system is twelve t one e qual t emperament sometimes abbreviated to 12-TET which is nowa.
Intervals may also be described as narrow and wide or small and large, consonant and dissonant or stable and unstable, weak and strong, simple and compound, vertical (or harmonic) and linear (or melodic), and, if linear as conjuct / steps or disjunct / skips. Simple intervals are those which lie within an octave and compound are those which are larger than a single octave. Thus a tenth is known as a compound third. Finally, intervals may be labelled with or modified by the addition of perfect, major, minor, augmented, and diminished before the number of notes apart (for instance, augmented fourth). Perfect intervals are never major or minor and major and minor intervals are never perfect. Major and minor intervals are one semitone above, or below, their minor and major counterparts, respectively (see minor second below). Augmented and diminished intervals are raised or lowered a step and any interval may be augmented or diminished and may even be double augmented or diminished. Linear intervals are successive pitches while vertical intervals are simultaneous. Steps are linear intervals between consecutive scale degrees while skips are not.
It is important to note that while intervals named by their harmonic functions, for instance, a major second, may be described by a ratio, cent, or integer, not every interval described by these more general terms may be described with the harmonic function name. For instance, all major seconds (in twelve tone equal temperament) are 200 cents, but not every interval of 200 cents is a major second. See: enharmonic.
