Editing Interval (music) (section)

==== Perfect ====
[[Image:Perfect intervals on C.png|thumb|Perfect intervals on C: {{audio|Unison on C.mid|PU}}, {{audio|Perfect fourth on C.mid|P4}}, {{audio|Perfect fifth on C.mid|P5}}, {{audio|Perfect octave on C.mid|P8}}]]
Perfect intervals are so-called because they were traditionally considered perfectly consonant,<ref name=Weber>
Definition of ''perfect consonance'' from
{{cite book |url=https://archive.org/details/bub_gb_20oBAAAAYAAJ |quote=perfect concord |first=Godfrey |last=Weber |title=General Music Teacher |year=1841}}
</ref>
although in Western classical music the perfect fourth was sometimes regarded as a less than perfect consonance, when its function was [[Counterpoint|contrapuntal]].{{Vague|date=February 2013}} Conversely, minor, major, augmented, or diminished intervals are typically considered less consonant, and were traditionally classified as mediocre consonances, imperfect consonances, or near-dissonances.<ref name=Weber/>

Within a [[diatonic scale]]{{efn|name=diatonic}} all unisons ('''P1''') and octaves ('''P8''') are perfect. Most fourths and fifths are also perfect ('''P4''' and '''P5'''), with five and seven semitones respectively. One occurrence of a fourth is augmented ('''A4''') and one fifth is diminished ('''d5'''), both spanning six semitones. For instance, in an E-major scale, the '''A4''' is between A and D{{music|sharp}}, and the '''d5''' is between D{{music|sharp}} and A.

The [[Inversion (music)#Intervals|inversion]] of a perfect interval is also perfect. Since the inversion does not change the [[pitch class]] of the two notes, it hardly affects their level of consonance (matching of their [[Harmonic series (music)|harmonics]]). Conversely, other kinds of intervals have the opposite quality with respect to their inversion. The inversion of a major interval is a minor interval, and the inversion of an augmented interval is a diminished interval.