Community hub
Recent from talks
Contribute something to knowledge base
Content stats: 0 posts, 0 articles, 0 media, 0 notes
Members stats: 0 subscribers, 0 contributors, 0 moderators, 0 supporters
Subscribers
Supporters
Contributors
Moderators
Enharmonic equivalence
In music, two written notes have enharmonic equivalence if they produce the same pitch but are notated differently. Similarly, written intervals, chords, or key signatures are considered enharmonic if they represent identical pitches that are notated differently. The term derives from Latin enharmonicus, in turn from Late Latin enarmonius, from Ancient Greek ἐναρμόνιος (enarmónios), from ἐν ('in') and ἁρμονία ('harmony').
The predominant tuning system in Western music is twelve-tone equal temperament (12 TET), where each octave is divided into twelve equal half-steps, or semitones; each half-step is both a chromatic semitone (a sharp or a flat) and a diatonic semitone (a minor step between two diatonic notes). The notes F and G are a whole step apart, so the note one semitone above F (F♯) and the note one semitone below G (G♭) indicate the same pitch. These written notes are enharmonic, or enharmonically equivalent. The choice of notation for a pitch can depend on its role in harmony; this notation keeps modern music compatible with earlier tuning systems, such as meantone temperaments. The choice can also depend on the note's readability in the context of the surrounding pitches. Multiple sharps or flats can produce other enharmonic equivalents; for example, F 
(double-sharp) is enharmonically equivalent to G♮.
When other tuning systems were in use, prior to the adoption of 12 TET, the term enharmonic referred to notes that were very close in pitch — closer than the smallest step of a diatonic scale — but not quite identical. In a tuning system without equal half steps, F♯ and G♭ do not indicate the same pitch, although the two pitches would be called enharmonically equivalent.
Sets of notes that involve pitch relationships — scales, key signatures, or intervals, for example — can also be referred to as enharmonic (e.g., in 12 TET the keys of C♯ major and D♭ major contain identical pitches and are therefore enharmonic). Identical intervals notated with different, enharmonically equivalent, written pitches are also referred to as enharmonic. The interval of a tritone above C may be written as a diminished fifth from C to G♭, or as an augmented fourth (C to F♯). In modern 12 TET, notating the C as a B♯ leads to other enharmonically equivalent notations, an option which does not exist in most earlier notation systems.
Enharmonic equivalents can be used to improve the readability of music, as when a sequence of notes is more easily read using sharps or flats. This may also reduce the number of accidentals required.
At the end of the bridge section of Jerome Kern's "All the Things You Are", a G♯ (the sharp 5th of an augmented C chord) becomes an enharmonically equivalent A♭ (the third of an F minor chord) at the beginning of the returning A section.
Beethoven's Piano Sonata in E Minor, Op. 90, contains a passage where a B♭ becomes an A♯, altering its overt musical function. The first two bars of the following passage contain a descending B♭ major scale. Immediately following this, the B♭s become A♯s, the leading tone of B minor:
Chopin's Prelude No. 15, known as the "Raindrop Prelude", features a pedal point on the note A♭ throughout its opening section.
Enharmonic equivalence
In music, two written notes have enharmonic equivalence if they produce the same pitch but are notated differently. Similarly, written intervals, chords, or key signatures are considered enharmonic if they represent identical pitches that are notated differently. The term derives from Latin enharmonicus, in turn from Late Latin enarmonius, from Ancient Greek ἐναρμόνιος (enarmónios), from ἐν ('in') and ἁρμονία ('harmony').
The predominant tuning system in Western music is twelve-tone equal temperament (12 TET), where each octave is divided into twelve equal half-steps, or semitones; each half-step is both a chromatic semitone (a sharp or a flat) and a diatonic semitone (a minor step between two diatonic notes). The notes F and G are a whole step apart, so the note one semitone above F (F♯) and the note one semitone below G (G♭) indicate the same pitch. These written notes are enharmonic, or enharmonically equivalent. The choice of notation for a pitch can depend on its role in harmony; this notation keeps modern music compatible with earlier tuning systems, such as meantone temperaments. The choice can also depend on the note's readability in the context of the surrounding pitches. Multiple sharps or flats can produce other enharmonic equivalents; for example, F (double-sharp) is enharmonically equivalent to G♮.
When other tuning systems were in use, prior to the adoption of 12 TET, the term enharmonic referred to notes that were very close in pitch — closer than the smallest step of a diatonic scale — but not quite identical. In a tuning system without equal half steps, F♯ and G♭ do not indicate the same pitch, although the two pitches would be called enharmonically equivalent.
Sets of notes that involve pitch relationships — scales, key signatures, or intervals, for example — can also be referred to as enharmonic (e.g., in 12 TET the keys of C♯ major and D♭ major contain identical pitches and are therefore enharmonic). Identical intervals notated with different, enharmonically equivalent, written pitches are also referred to as enharmonic. The interval of a tritone above C may be written as a diminished fifth from C to G♭, or as an augmented fourth (C to F♯). In modern 12 TET, notating the C as a B♯ leads to other enharmonically equivalent notations, an option which does not exist in most earlier notation systems.
Enharmonic equivalents can be used to improve the readability of music, as when a sequence of notes is more easily read using sharps or flats. This may also reduce the number of accidentals required.
At the end of the bridge section of Jerome Kern's "All the Things You Are", a G♯ (the sharp 5th of an augmented C chord) becomes an enharmonically equivalent A♭ (the third of an F minor chord) at the beginning of the returning A section.
Beethoven's Piano Sonata in E Minor, Op. 90, contains a passage where a B♭ becomes an A♯, altering its overt musical function. The first two bars of the following passage contain a descending B♭ major scale. Immediately following this, the B♭s become A♯s, the leading tone of B minor:
Chopin's Prelude No. 15, known as the "Raindrop Prelude", features a pedal point on the note A♭ throughout its opening section.