Neapolitan sixth chord.

The first inversion of the major triad built on the flattened second degree of the scale; in C major or minor, F–A–D. It usually precedes a V–I cadence and it functions like a subdominant (in German chord analysis it can be described as the Leittonwechselklang of the minor subdominant). It is associated with the so-called ‘Neapolitan school’, which included Alessandro Scarlatti, Pergolesi, Paisiello, Cimarosa and other important 18th-century composers of Italian opera; but it seems to have been an established if infrequent harmonic practice by the end of the 17th century, being used by Carissimi, Corelli and Purcell. It was also a favourite idiom among composers in the Classical period, especially Beethoven, who extended its use to root-position and second-inversion chords (examples include the opening of the String Quartet op.95 and the second movement of the Hammerklavier Sonata).

WILLIAM DRABKIN