Clockwatcher,most of the tunes are in the following modes,Dorian [flat3 flat7]Mixolydian[flat 7]Aeolian[flat3,flat7 flat 6]and major[ionian],they are not in minor keys.
there are two minor keys Harmonic and melodic which were you referring to.
they may be harmonised with minor or [modal chords,dyads comprising notes 1 and 5].
many interesting tunes have one section in the major and another in the dorian,or other combinations.
here is a set dance Rodneys Glory,that is a wonderful dance but it is not in the major key. Dick Miles