In the key of C major the second degree of the scale (D) gets lowered a half step to D-flat. Then just build a major triad... D flat, F , A flat. ... The Neapolitan 6th chord is an expressive alternative to the ii6 chord, and most often found in the minor key, although there are plenty of examples of it in major. Its genesis is very simple. Take the progression iiº6 - V7 - i in a minor key, and use the lowered second degree of the scale for the supertonic triad.