A Little Help With Theory

I was just wondering if someone knew the answer to this. When writing neapolitan chords, augmented sixth chords (Italian, French, and German), common-tone diminished seventh chords, and chords with a chromatic mediant relationship (or doubly-chromatic mediant relationship) where there is no modulation, which scale or collection of notes can you play over these chords? Or, in other words, what notes do I use to construct my melody/melodies above these chords other than the notes that the chord/chords are constructed out of?