Harmonic Minor.../...Melodic Minor Scales...

[losthobos]

Perhaps someone can help me out here...my theory is pretty dud...
i understand A minor is relative minor to C ...and has same notes , used simply over Am,Dm Em progression
but where is Harmonic Minor used..i'm guessing over Am, Dm E7 type progs as the G sharp is present..... which brings me to the
Melodic Minor which has an added f sharp as well as the G sharp and thus implies the chords maybe Am, D, E7 etc though i'm struggling to understand why descending it reverts to the Relative minor of C to descend... i like the slightly Arabic feel to this scale but just enquiring to further my knowledge
thanks for any help

 

[Anyanka]

As far as I understand, melodic minor is primarily used by singers. When I had piano lessons, my teacher told me to only practice the harmonic minors, and I've stuck with that habit on the accordion too.