Musical harmony stuff. Bet you're not interested.
I have a peculiar love for the Neapolitan sixth - I don't know why. So I started thinking about its origin.
Not in Arnold Schönberg's tractise, neither in the Walter Piston one (at least in the '59 edition, which is the only one I have at my disposal - I would be interested to read something from Paul Hindemith about this subject...) there's a convincing explanation to me. Schönberg claims its derivation from a subdominant (minor) harmony, whose real link to the original tonality I've always be greatly dubious (all in all, almost the totality of the chords are much simpler to be defined reinterpreting them through the minor form of the very same tonality - excluding the ones with the lowered second degree, whose main representative is the Neapolitan sixth!), whereas the Piston simply declares a descending alteration of the fundamental, a fact which…