Glossary, Fourth
   
Glossary
Acoustic
Acoustics
Ancohemitonic

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Atonal Theory

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Atritonic

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Augmented
Avoid Note
Bebop
Blues
Cardinality

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Cardinality Equivalence

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Cent
Chord
Chord Formula
Chord Type
Chromatic Cluster

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Chromatic Scale
Clock Diagram

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Cluster-free

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Cohemitonic

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Common Practice
Compatibility
Complement

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Consonance
Diatonic
Diminished
Double Augmented Hexatonic
Double Diminished (Octatonic)
Eleventh
Enharmonic Equivalent
Evenness

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Fifth
Forte Number

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Fourth
Guitar
Harmonic Major
Harmonic Minor
Harmony
Interval
Interval Class

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Interval Content

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Inversion
Involution

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Jazz
Jazz Theory
Key
Keyboard
Lewin-Quinn FC-components

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Limited Transposition

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M-Relation

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Major
Melody
Minor
Mode
Ninth
Note
OC-Equivalence

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OPC-Equivalence

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OPTC-Equivalence

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OPTIC-Equivalence

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OPTIC/K-Equivalence

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OTC-Equivalence

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Octatonic
Octave
Octave-Equivalence

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Other Scales
Parallel Key
Pentatonic
Permutation Equivalence

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Piano
Pitch
Pitch Class

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Playing Outside
Prime Form

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Quartal

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Reharmonization
Relative Key
Rhythm
Roman Numeral Function
Root
Scale
Second
Semitone
Set Class

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Seventh
Sixth
Slash Chords
Suspended
Symmetry

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Tenth
Tertiary
Third
Thirteenth
Tonality
Tonic
Transposition
Triad
Tritone
Tritonic

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Tuning Systems
Twelfth
Twelve-tone Equal Temperament
Unison
Voice Leading
Whole Tone
Whole-Tone Scale
Z-Relation

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Fourth

Glossary

The fourth or perfect fourth is a consonant interval with a ratio very close to 4:3. See also diminished fourth and augmented fourth intervals and Pitch & Intervals. In the context of chords, the degree is usually notated as an eleventh.

The inversion of a perfect fourth is the perfect fifth, so they share an interval class.

Referring to roman numeral function, “fourth” can mean the IV chord of a key.