A Picardy third, Picardy cadence or, in French, tierce picarde, is a major chord of the tonic at the end of a musical section that is either modal or in a minor key. This is achieved by raising the third of the expected minor triad by a semitone to create a major triad, as a form of resolution.
For example, instead of a cadence ending on an A minor chord containing the notes A, C, and E, a Picardy third ending would consist of an A major chord containing the notes A, C♯, and E. Note that the minor third between the A and C of the A minor chord has become a major third in the Picardy third chord.
Even in instrumental music, the picardy third retains its expressive quality: it is the "happy third". ... Since at least the beginning of the seventeenth century, it is no longer enough to describe it as a resolution to the more consonant triad; it is a resolution to the happier triad as well. ... The picardy third is absolute music's happy ending. Furthermore, I hypothesize that in gaining this expressive property of happiness or contentment, the picardy third augmented its power as the perfect, most stable cadential chord, being both the most emotionally consonant chord, so to speak, as well as the most musically consonant.
According to Deryck Cooke, "Western composers, expressing the 'rightness' of happiness by means of a major third, expressed the 'wrongness' of grief by means of the minor third, and for centuries, pieces in a minor key had to have a 'happy ending' - a final major chord (the 'tierce de Picardie') or a bare fifth."
The Picardy third does not necessarily occur at the end of a section: it can be found at any perfect cadence or plagal cadence where the prevailing key is minor. As a harmonic device, the Picardy third originated in Western music in the Renaissance era.
What makes this a Picardy cadence is shown by the red natural sign. Instead of the expected B-flat (which would make the chord minor) the accidental gives us a B natural, making the chord major.
The origins of the term are obscure. An idea that was repeated as fact for some time, but turns out to have no provable basis, was that expounded by Jean-Jacques Rousseau in his Dictionnaire de Musique (1767): that this form of ending survived longest in church music, and due to the great number of cathedrals in the historical French province of Picardy. More plausible is the idea that the North of France, and Flanders, were influential in the development of contrapuntal music in the fifteenth century.
Robert Hall hypothesizes that, instead of deriving from the Picardy region of France, it comes from the Old French word "picart", meaning "pointed" or "sharp" in northern dialects, and thus refers to the musical sharp that transforms the minor third of the chord into a major third.
In medieval music, such as that of Machaut, neither major nor minor thirds were considered stable intervals, and so cadences were typically on open fifths. As a harmonic device, the Picardy third originated in Western music in the Renaissance era. By the early seventeenth century, its use had become established in practice in music that was both sacred, (as in the Schutz example above) and also secular:
Examples of the Picardy third can be found throughout the works of J.S. Bach and his contemporaries, as well as earlier composers such as Thoinot Arbeau and John Blow. Many of J.S.Bach's minor key chorales end with a cadence featuring a final chord in the major:
In his book Music and Sentiment, Charles Rosen shows how J.S.Bach makes use of the fluctuations between minor and major to convey feeling in his music. Rosen singles out the Allemande from the keyboard Partita in B flat, BWV825 to exemplify "the range of expression then possible, the subtle variety of inflections of sentiment contained with a well-defined framework." The following passage from the first half of the piece starts in F major, but then, in bar 15, "Turning to the minor mode with a chromatic bass and then back to the major for the cadence adds still new intensity."
Many passages in Bach's religious works follow a similar expressive trajectory involving major and minor keys that may sometimes take on a symbolic significance. For example, David Humphreys (1983, p.23) sees the "languishing chromatic inflections, syncopations and appoggiaturas" of the following episode from the St Anne Prelude for organ, BWV552 from Clavier-Übung III as "showing Christ in his human aspect. Moreover the poignant angularity of the melody, and in particular the sudden turn to the minor, are obvious expressions of pathos, introduced as a portrayal of his Passion and crucifixion":
Notably, J. S. Bach's two books of The Well-Tempered Clavier, composed in 1722 and 1744 respectively, differ considerably in their application of Picardy thirds, which occur unambiguously at the end of all of the minor-mode preludes and all but one of the minor-mode fugues in the first book. In the second book, however, fourteen of the minor-mode movements end on a minor chord, or occasionally, on a unison. Manuscripts vary in many of these cases.
Philip Radcliffe says that the dissonant harmonies here "have a vivid foretaste of Schumann and the way they gently melt into the major key is equally prophetic of Schubert."
At the end of his opera Don Giovanni, Mozart uses the switch from minor to major to considerable dramatic effect: "As the Don disappears, screaming in agony, the orchestra settles in on a chord of D major. The change of mode offers no consolation, though: it is more like the tierce de Picardie, the 'Picardy third' (a famous misnomer derived from tierce picarte, 'sharp third'), the major chord that was used to end solemn organ preludes and toccatas in the minor keys in days of old." The fierce C minor drama that pervades the Allegro con brio ed appassionato movement from Beethoven's last Piano Sonata, Op.111, dissipates as the prevailing tonality turns to the major in its closing bars "in conjunction with a concluding diminuendo to end the movement, somewhat unexpectedly, on a note of alleviation or relief."
The switch from minor to major was a device used frequently and to great expressive effect by Schubert in both his songs and instrumental works. In his book on the song cycle Winterreise, singer Ian Bostridge speaks of the "quintessentially Schubertian effect in the final verse" of the opening song "Gute Nacht", "as the key shifts magically from minor to major."
Susan Wollenberg describes how the first movement of Schubert's Fantasia in F minor for piano four-hands, D940 "ends in an extended Tierce de Picardie." The subtle change from minor to major occurs in the bass at the beginning of bar 103:
In the Romantic era, those of Chopin's nocturnes that are in a minor key almost always end with a Picardy third. A notable structural employment of this device occurs with the finale of the Tchaikovsky Fifth Symphony, where the motto theme makes its first appearance in the major mode.
According to James Bennighof: "Replacing an expected final minor chord with a major chord in this way is a centuries-old technique--the raised third of the chord, in this case G♯ rather than G natural,[verification needed] was first dubbed a 'Picardy third' ("tierce de Picarde") in print by Jean-Jacques Rousseau in 1797 ... to express [the idea that] hopefulness might seem unremarkable, or even clichéd."