A Picardy third (//) (French: tierce picarde), also known as a Picardy cadence, 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.
Musicologist Peter Kivy writes:
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."
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.
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 Schütz example above) and 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 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 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, BWV 825 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, BWV 552 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, 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, D 940, "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."
- (Unknown) – "Coventry Carol" (written not later than 1591). Modern harmonisations of this carol include the famously distinctive finishing major Picardy third in the melody, but the original 1591 harmonisation went much further with this device, including Picardy thirds at seven of the twelve tonic cadences notated, including all three such cadences in its chorus.
- The Beatles – "I'll Be Back", from the soundtrack album of the film A Hard Day's Night. Ian MacDonald speaks of the way "Lennon is harmonised by McCartney in shifting major and minor thirds, resolving on a Picardy third at the end of the first and second verses".
- Beethoven – Hammerklavier, slow movement
- Brahms – Piano Trio No. 1, scherzo
- Sarah Connor – "From Sarah with Love", final cadence
- Coots and Gillespie, "You Go to My Head". Ted Gioia describes the song as starting "in the major key, but from the second bar onward, Mr. Coots seems intent on creating a feverish dream quality tending more to the minor mode" before finally reaching a cadence in the major.
- Dvořák – New World Symphony, finale
- Bob Dylan – "Ain't Talkin'", the final song on Modern Times (2006), is played in E minor but ends (and ends the album) with a ringing E major chord.
- Roberta Flack – "Killing Me Softly with His Song" ending and resolution. According to Flack: "My classical background made it possible for me to try a number of things with [the song's arrangement]. I changed parts of the chord structure and chose to end on a major chord. [The song] wasn't written that way."
- Joni Mitchell – "Tin Angel", from Clouds (1969); the Picardy third lands on the lyric "I found someone to love today". According to Katherine Monk, the Picardy third in this song, "suggests Mitchell is internally aware of romantic love's inability to provide true happiness but, gosh darn it, it's a nice illusion all the same."
- Donna Summer – “I Feel Love” (1977) alternates throughout with an accompaniment of "synth swirls: major and minor; it’s basically a version of what Franz Schubert did for his whole career." 
- Percy Scholes (ed.), The Oxford Companion to Music: Self-indexed and with a Pronouncing Glossary and Over 1,100 Portraits and Pictures, ninth edition, completely revised and reset and with many additions to text and illustrations (London and New York: Oxford University Press, 1955), pp. 1027–28.
- Peter Kivy, Osmin's Rage: Philosophical Reflections on Opera, Drama, and Text, with a New Final Chapter (Ithaca and London: Cornell University Press, 1999), p. 289. ISBN 978-0-8014-8589-3.
- Deryck Cooke, The Language of Music (London and New York: Oxford University Press, 1959), p. 57.
- Denise LaGiglia and Anna Belle O'Shea, The Liturgical Flutist: A Method Book and More (Chicago, Illinois: GIA Publications, 2005), p. 166. ISBN 978-1-57999-529-4.
- Robert A. Hall, Jr., "How Picard was the Picardy Third?", Current Musicology 19 (1975): pp. 78–80.
- Bruce Benward and Marilyn Nadine Saker, Music in Theory and Practice: Volume II, eighth edition (Boston: McGraw-Hill, 2009), p. 74. ISBN 978-0-07-310188-0.
- Charles Rosen, Music and Sentiment (New Haven and London: Yale University Press, 2010), p. 45.
- Humphreys, D. (1983). The Esoteric structure of Bach's Clavierübung III, p. 25. University of Cardiff Press.
- Butler, H. Joseph. "Emulation and Inspiration: J. S. Bach's Transcriptions from Vivaldi's L'estro armonico" (2011), p. 21.
- Oxford Companion to Music, tenth edition, edited by Percy A. Scholes and John Owen Ward (London and New York: Oxford University Press, 1970).[full citation needed]
- Radcliffe, P. (1978). Mozart Piano Concertos, p. 52. London: British Broadcasting Corporation.
- Taruskin, R. (2010). The Oxford History of Western Music: Music in the seventeenth and Eighteenth centuries, p. 494. Oxford University Press.
- Taruskin, R. (2010). The Oxford History of Western Music: Music in the Seventeenth and Eighteenth Centuries, p. 730. Oxford University Press.
- Ian Bostridge (2015). Schubert's Winter Journey, p. 7 London: Faber and Faber.
- Wollenberg, S. (2011). Schubert's Fingerprints: Studies in the Instrumental Works, p. 42. London, Routledge.
- James Bennighof, "The Words and Music of Joni Mitchell", Santa Barbara: Praeger, 2010.[page needed]
- Coventry Carol Archived 2016-09-11 at the Wayback Machine at the Choral Public Domain Library. Accessed 2016-09-07.
- Thomas Sharp, A Dissertation on the Pageants Or Dramatic Mysteries Anciently Performed at Coventry (Coventry: Merridew and Son, 1825), p. 116.
- Ian MacDonald, Revolution in the Head: The Beatles Records and the Sixties (London: Pimlico, 2005): p. 119.
- Robert S. Hatten, Musical Meaning in Beethoven: Markedness, Correlation, and Interpretation (Bloomington: Indiana University Press, 1994), p. 39. ISBN 0-253-32742-3. First paperback reprint edition 2004. ISBN 978-0-253-21711-0.
- Johannes Brahms, Complete Piano Trios ([full citation needed]: Dover Publications, 1926),[page needed]. ISBN 048625769X.
- Walter Everett, "Pitch Down the Middle", in Expression in Pop-Rock Music, second edition, edited by[full citation needed] (Oxford and New York: Oxford University Press, 2008):[page needed]
- Gioia, T. (2012). The Jazz Standards: A Guide to the Repertoire, p. 468. Oxford University Press.
- Antonín Dvořák, Symphonies Nos. 8 and 9 (Dover Publications, 1984), pp. 257–258. ISBN 048624749X.
- See "Ain't Talkin'" in songs list at https://dylanchords.info. Archived 2019-09-26 at the Wayback Machine The guitar part is played in Em with a capo on the 4th fret, so the song sounds in the key of G♯ minor.
- Toby Cresswell, 1001 Songs (Pahran, Austria: Hardie Grant Books, 2005), p. 388, ISBN 978-1-74066-458-5.
- Katherine Monk, Joni: The Creative Odyssey of Joni Mitchell (Vancouver: Greystone, 2012) p. 73. ISBN 9781553658375
- Tom Service (2019) "Riffs, Loops and Ostinati", a programme in the series The Listening Service, BBC Radio 3, 27 January. https://www.bbc.co.uk/sounds/play/m00022nx Accessed 29 January 2019.
- Latham, Alison (ed.). 2002. "Tierce de Picardie (Fr., ‘Picardy 3rd’)". The Oxford Companion to Music. Oxford and New York: Oxford University Press. ISBN 978-0-19-866212-9.
- Ruff, Lillian M. 1972. "Josquin Des Pres: Some Features of His Motets". The Consort: Annual Journal of the Dolmetsch Foundation 28:106–18.
- Rushton, Julian. 2001. "Tierce de Picardie [Picardy 3rd]". The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell. London: Macmillan Publishers.
- Rutherford-Johnson, Tim, Michael Kennedy), and Joyce Bourne Kennedy (eds.). 2012. "Tierce de Picardie". The Oxford Dictionary of Music, sixth edition. Oxford and New York: Oxford University Press. ISBN 978-0-19-957810-8.