Lox, it is rare that a minor tune is not predominantly based on (and notated according to) the natural minor scale. The melodic and harmonic variants are simply common patterns or digressions that are used simultaneously with it--and they're indicated with accidentals. The harmonic structure is also derived from the natural minor scale, even if it too sometimes deviates from the base note set. A tune whose fundamental basis is the harmonic or (ascending) melodic minor pattern--or some other deviation from the natural minor--is not really minor as we know it.

Which raises an interesting point: the term "relative key" means a key in the same set of key/mode pairs whose scales precisely share the same absolute pitch set (extended by octave translations). They will have the same key signature but different tonal centers and modes (base interval patterns relative to the tonic). I don't believe it makes sense to talk about "relative keys" for scales which have no common note set, as between a major key and the Arabic scale discussed wrt "Hava Nagila". What is then the basis for the relation? It cannot just be the perception of majorness and minorness according to the magic sixth formula: The Dorian relative of C major is D Dorian, not A Dorian, even though Dorian is minorish in having a minor tonic chord and a minor seventh. And the Arabic scale, which sounds "minorish" to our ears, has a major tonic chord though in fact its closest liturgical counterpart would be Phrygian, differing only in the major third! It is the liturgical scale pattern which defines the relative key relations among the seven modes--and only those modes.