Enharmonic in the context of A (musical note)

In music theory, an interval is a difference in pitch between two sounds. An interval may be described as horizontal, linear, or melodic if it refers to successively sounding tones, such as two adjacent pitches in a melody, and vertical or harmonic if it pertains to simultaneously sounding tones, such as in a chord.

In Western music, intervals are most commonly differencing between notes of a diatonic scale. Intervals between successive notes of a scale are also known as scale steps. The smallest of these intervals is a semitone. Intervals smaller than a semitone are called microtones. They can be formed using the notes of various kinds of non-diatonic scales. Some of the very smallest ones are called commas, and describe small discrepancies, observed in some tuning systems, between enharmonically equivalent notes such as C♯ and D♭. Intervals can be arbitrarily small, and even imperceptible to the human ear.

In music, a pitch class (p.c. or pc) is a set of all pitches that are a whole number of octaves apart; for example, the pitch class C consists of the Cs in all octaves. "The pitch class C stands for all possible Cs, in whatever octave position." Important to musical set theory, a pitch class is "all pitches related to each other by octave, enharmonic equivalence, or both." Thus, using scientific pitch notation, the pitch class "C" is the set

Although there is no formal upper or lower limit to this sequence, only a few of these pitches are audible to humans. Pitch class is important because human pitch-perception is periodic: pitches belonging to the same pitch class are perceived as having a similar quality or color, a property called "octave equivalence".

There is a long tradition in classical music of writing music in sets of pieces that cover all the major and minor keys of the chromatic scale. These sets typically consist of 24 pieces, one for each of the major and minor keys (sets that comprise all the enharmonic variants include 30 pieces).

Examples include Johann Sebastian Bach's The Well-Tempered Clavier and Frédéric Chopin's 24 Preludes, Op. 28. Such sets are often organized as preludes and fugues or designated as preludes or études. Some composers have restricted their sets to cover only the 12 major keys or the 12 minor keys; or only the flat keys (Franz Liszt's Transcendental Études) or the sharp keys (Sergei Lyapunov's Op. 11 set). In yet another type, a single piece may progressively modulate through a set of tonalities, as occurs in Ludwig van Beethoven's 2 Preludes through all the Major Keys, Op. 39.

C or Do is the first note of the C major scale, the third note of the A minor scale (the relative minor of C major), and the fourth note (G, A, B, C) of the Guidonian hand, commonly pitched around 261.63 Hz. The actual frequency has depended on historical pitch standards, and for transposing instruments a distinction is made between written and sounding or concert pitch. It has enharmonic equivalents of B♯ and D.

In English the term Do is used interchangeably with C only in the context of fixed Do solfège; in the movable Do system Do refers to the tonic of the prevailing key.

E is the third note and the fifth semitone of the C major scale, and mi in fixed-do solfège. It has enharmonic equivalents of F♭ [(F-flat) which is by definition a diatonic semitone above E♭] and D (D-double sharp), amongst others.

When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of Middle E (E₄) is approximately 329.628 Hz. See pitch (music) for a discussion of historical variations in frequency.

E♭ (E-flat) or mi bémol is the fourth semitone of the solfège.

It lies a diatonic semitone above D and a chromatic semitone below E, thus being enharmonic to D♯ (D-sharp) or re dièse. In equal temperament it is also enharmonic with F (F-double flat). However, in some temperaments, D♯ is not the same as E♭. E♭ is a perfect fourth above B♭, whereas D♯ is a major third above B.

In Western classical music, an augmented fifth (Play) is an interval produced by widening a perfect fifth by a chromatic semitone. For instance, the interval from C to G is a perfect fifth, seven semitones wide, and both the intervals from C♭ to G, and from C to G♯ are augmented fifths, spanning eight semitones. Being augmented, it is considered a dissonant interval.

Its inversion is the diminished fourth, and its enharmonic equivalent is the minor sixth.

D is a musical note a whole tone above C, and is known as Re within the fixed-Do solfege system. Its enharmonic equivalents are C (C-double sharp) and E (E-double flat). It is the third semitone of the solfège.

When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of middle D (D₄) is approximately 293.665Hz. See pitch for a discussion of historical variations in frequency.

B-flat minor is a minor scale based on B♭, consisting of the pitches B♭, C, D♭, E♭, F, G♭, and A♭. Its key signature has five flats. Its relative major is D-flat major and its parallel major is B-flat major. Its enharmonic equivalent, A-sharp minor, which would contain seven sharps, is not normally used.

The B-flat natural minor scale is:

In music, 'relative keys' are the major and minor scales that have the same key signatures (enharmonically equivalent), meaning that they share all of the same notes but are arranged in a different order of whole steps and half steps. A pair of major and minor scales sharing the same key signature are said to be in a relative relationship. The relative minor of a particular major key, or the relative major of a minor key, is the key which has the same key signature but a different tonic. (This is as opposed to parallel minor or major, which shares the same tonic.)

For example, F major and D minor both have one flat in their key signature at B♭; therefore, D minor is the relative minor of F major, and conversely F major is the relative major of D minor. The tonic of the relative minor is the sixth scale degree of the major scale, while the tonic of the relative major is the third degree of the minor scale. The minor key starts three semitones below its relative major; for example, A minor is three semitones below its relative, C major.

In musical tuning, the Pythagorean comma (or ditonic comma), named after the ancient mathematician and philosopher Pythagoras, is the small interval (or comma) existing in Pythagorean tuning between two enharmonically equivalent notes such as C and B♯, or D♭ and C♯. It is equal to the frequency ratio (1.5)⁄2 = 531441⁄524288 ≈ 1.01364, or about 23.46 cents, roughly a quarter of a semitone (in between 75:74 and 74:73). The comma that musical temperaments often "temper" is the Pythagorean comma.

The Pythagorean comma can be also defined as the difference between a Pythagorean apotome and a Pythagorean limma (i.e., between a chromatic and a diatonic semitone, as determined in Pythagorean tuning); the difference between 12 just perfect fifths and seven octaves; or the difference between three Pythagorean ditones and one octave. (This is why the Pythagorean comma is also called a ditonic comma.)