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The Andalusian cadence (diatonic phrygian tetrachord) is a term adopted from flamenco music for a chord progression comprising four chords descending stepwise: iv–III–II–I progression with respect to the Phrygian mode or i–VII–VI–V progression with respect to the Aeolian mode (minor). It is otherwise known as the minor descending tetrachord. Traceable back to the Renaissance, its effective sonorities made it one of the most popular progressions in classical music.

The Andalusian cadence can be regarded as a modulation between the Phrygian mode of a Major parent scale and the Phrygian Dominant mode of a Harmonic Minor scale, e.g. E, F, G (phrygian) or G (phrygian dominant), A, B, C, D.

Despite the name it is not a true cadence (i.e., occurring only once, when ending a phrase, section, or piece of music); it is most often used as an ostinato (repeating over and over again). It is heard in rock songs such as "Runaway" by Del Shannon.

Origins

A popular melodic pattern of Ancient Greece offers a possible starting point for the Andalusian cadence. Called the Diatonic tetrachord, the sequence resembles the bass line of the chord progression developed centuries later. Some theorists consider that the same structure may have occurred earlier in Judah. A sequence more or less close to the Greek tetrachord structure might have been known to the Moors in Southern Spain and spread from there through Western Europe. The French troubadours were influenced by the Spanish music. This work was first published in the Eighth Book of Madrigals (1638).

The progression resembles the first four measures of the 15th century Passamezzo antico; i – VII – i – V. The use of the VI chord may suggest a more recent origin than the Passamezzo antico since the cadences i – VII and VII – i were popular in the late Middle Ages and early Renaissance, (see also double tonic) while VII – VI arose as a result of advancement in music theory. However, the absence of the leading tone from the VII chord suggests that the progression originated before the tonal system in the modal approach of the time of Palestrina, where the tonic must be approached from chord V whereas typical Baroque style would have avoided the flat VII and introduced dominant chords (VII or V chords, to form cadences resolving upon chord i).

Analysis

Melody

A minor seventh would be added to the dominant "V" chord to increase tension before resolution (V<sup>7</sup>–i). the latter mentioned above), that is to be found as the upper tetrachord of a natural minor scale (for A minor, they are: A G F E).

A remarkable fact about tetrachords was noticed since the Ancient times and rediscovered in early Renaissance: when a tetrachord features a semitone (half-step) between two of its tones, it is the semitone that will determine the melodic tendency of the given tetrachord or mode (when combining tetrachords). If the semitone falls between the highest two steps, the melody tends to be ascending (e.g. major scales); a semitone between the lowest tones in the tetrachord involves a melody "inclined" to descend. This said, the Phrygian tetrachord, borrowed from traditional music of Eastern Europe and Anatolia,File:Simple Andalusian cadence.mid]]

A rigorous analysis should note that many chord progressions are likely to come from an epoch prior to early Baroque (usually associated with birth of tonality). Since tonality took the first chord in the progression for a tonic ("i"), the Phrygian notation (modal) of the cadence writes as following: iv – III – II – I (or, more commonly, but less correctly, iv – III – II – I however, step three switches between major and minor third, an equivalent to the subtonic/leading tone conflict in the tonal acceptation.) Thus, the "iv" corresponds to a subdominant chord, while "III" is the mediant and "I" is the tonic. The "II" chord has a dominant function,

Harmonic peculiarities

The tonal system sets three main functions for the diatonic tertian chords: tonic (T), dominant (D) and subdominant (SD). Any sequence through different functions is allowed (e.g. T→D, SD→D), except for D→SD. A tonal scale's degrees are as following: "I" and "VI" are tonic chords (of which, "I" is stronger; all final cadences end in "I"), "V" and "VII" are dominant function (both feature the leading tone and "V" is more potent), "IV" and "II" are subdominant function chords ("IV" is stronger).

An interesting variation/extension on the cadence appears in the rideout of The Beatles' "I Am The Walrus" (beginning at 3:17). (This rideout is itself an example of a Shepard scale, in which a bass line and a treble line move unceasingly in contrary motion.) The rideout begins with what might be called a double Andalusian cadence in the bass: E, D, C, B; A, G, F, E. Yet after these eight measures, the Andalusian 'cycle' is one step "off", and the new 'cadence' is D, C, B, A. Normally, continuing this procedure, it would take until the fifth repetition of this two-cadence cycle to reach another Andalusian tetrachord (with intervals whole, whole, half). But the Beatles and producer George Martin pull off a deft bit of legerdemain during this second set of tetrachords: they break the cycle while apparently continuing it. At 3:55, Ringo Starr plays a fill, changing the pattern and marking the next chord change (to D) as an arrival. After this, the four-chord pattern is apparently shifted to the alternate pattern D, C, B, A; G, F, E, D (with intervals whole, half, whole); yet through subtle accentual maneuvering, this eight-change pattern 'fits' within seven changes, and D somehow appears to always begin a cycle. (One might also maintain that any regularity is now broken entirely, and the changes have become an unending Möbius strip.)

Modern flamenco usage

The integration of the traditional Andalusian cadence and Renaissance-style practices of musical composition and song are evident in modern musical genres such as rock and pop. Flamenco music, a style of music and dance that was popularized in the Andalusian regions of Spain, has also been incorporated into modern pop and rock music. Specific examples include the usage of the cadence in "La leyenda del tiempo" by Camarón de la Isla. Other recent uses of the cadence are apparent in flamenco inspired rock songs such as "Ya no me asomo de la reja", 'La que vive en la Carrera", and the bassline of "Negras las intenciones".