Why Doesn’t a Picardy Third Erase the Minor Mode?

A minor-key work that ends on a major tonic chord is commonly said to use a Picardy third. The physical change is tiny: the third of the final tonic chord rises by a semitone. In C minor, for example, the ending moves from C–E-flat–G to C–E–G. Only one note changes, yet the close can feel as though a shaft of light has entered.

That does not mean the music has simply turned from sad to happy. Major, minor and emotion do not form such a neat code. The Picardy third has force precisely because the preceding minor mode remains in memory. The major third does not delete the journey; it reinterprets it over the same tonic. If the whole passage had already been in C major, the E natural would not carry the same turn.

Bach’s Prelude and Fugue in C minor, BWV 847, from Book I of The Well-Tempered Clavier both close with a major tonic chord. At the piano, it is tempting to spotlight the final E natural and make the ending sound sugary. A better approach is to preserve the grounding C and allow the changed third to register on its own. Touch, duration and pedal may open the space, but need not proclaim a victory. What matters is that the tonal centre has not moved, while the colour of the ending changes at the last moment.

https://imslp.org/wiki/Prelude_and_Fugue_in_C_minor%2C_BWV_847_%28Bach%2C_Johann_Sebastian%29
https://www.loc.gov/resource/muspre1800.101611/?sp=428
https://arxiv.org/abs/2103.09709