The Neapolitan Sixth (♭II6)
The Neapolitan sixth is a major triad built on the lowered second scale degree (ra, ♭2). It functions as a chromatic predominant — a colorful substitute for a minor iv or iiº — and almost always appears in first inversion, which is why we label it ♭II6.
Its characteristic voice leading is the descent of ra (♭2) down to ti (the leading tone) as the chord resolves to V. Think of ♭II6 as a chromatically lowered version of a iiº6 chord: same scaffolding, darker color.
The "Neapolitan" name nods to 18th-century Naples, but the historical link is thin — composers across Europe used the chord freely. In practice ♭II6 frequently goes straight to V (often through a cadential 6/4), and a common intensification inserts an applied chord: ♭II6 – viiº7/V – V.
