A characteristic melodic feature of the Neapolitan 6th is the use of a chromatic upper and lower neighbour around the tonic note.

The Neapolitan 6th chord is often combined with a bass-line which uses (1), (4) and (5) of the scale.

When we play this combination we clearly hear during the dominant a 4-3 movement in the upper voice

In a four-part keyboard setting:

Compared with II6 in minor:

Compared with N6 in major:

Compared with II6 in major: