Surely one minor scale is enough! It would certainly make things easier, but in a lot of cases it would not sound as easy on the ear. OK, so we need to use the notes of the major scale in a way that makes the whole thing sound sad or haunting.

Playing the major scale pitches downwards starting on the 6th degree for an octave (the natural or relative minor) does produce a sad sound but has two serious drawbacks. Firstly, the same scale doesn