Many of us knows how to play the major scales but some are confused over the minor scales. There are 3 types of minor scales: Harmonic, melodic & natural. Over here, I'll briefly discuss the relationship of the major & minor scales. (Do not get confused with the term harmonic & melodic as in harmonic & melodic intervals) Here, we will use A major and different forms of A minor as example.
Major Scale in the key of A (accending/going up)
A, B, C#, D, E, F#, G#, A (T, T, S, T, T, T, S)
Major scales are the same when played accending and decending(going down)
Harmonic Minor Scale in the key of A
To play a harmonic minor scale, simply flat(b) the 3rd and 6th degree of a major scale. This case, A is the 1st, B is the 2nd and C# is the 3rd and etc.
A, B, C, D, E, F, G#, A
Harmonic minor scales are the same accending and decending.
Melodic Minor Scale in the key of A
Accending A, B, C, D, E, F#, G#, A (Flat the 3rd of a major; C# becomes C)
Decending A, G, F, E, D, C, B, A (Flat the 3rd, 6th & 7th of a major scale)
Natural Minor Scale in the key of A
A, B, C, D, E, F, G, A (Flat the 3rd, 6th & 7th of a major scale)
Natural Minor Scale is the same accending and decending. Notice that it is the same form as a melodic minor decending. (Not tested in major exam boards, can ignore this form.)
Conclusion:
On a minor scale, the 3rd degree is always flatten(b). To play a simplfied version of a minor scale, flat the 3rd or mediant of a major scale.
Legend
# Sharp
b Flat
Hope this helps.