Melodic minor in practice
Use the raised sixth and seventh going up and natural minor going down.
Different up and down
Going up, melodic minor raises two degrees: VI and VII. Going down the raised notes return to normal, and natural minor sounds.
In A minor: up A, B, C, D, E, F♯, G♯, A; down A, G, F, E, D, C, B, A.
A melodic minor, up and down
Practice: Which minor? (1)
Practice: What changes?
Why two degrees
In harmonic minor there is an augmented second between degrees VI and VII. In a melody this step sounds harsh and "oriental". Raising degree VI smooths it to a whole tone while keeping the leading note.
Going down the leading note is not needed: the melody is not reaching up to the tonic, so the raised notes are dropped. In practice that is how it is written: a line rising to the tonic uses the raised degrees; a line falling from the tonic does not.
A harmonic minor: E – F – G♯ – A
A melodic minor: E – F♯ – G♯ – A
Melodic minor is recognised by its upper half: going up, it is the same as in major. The lower half of the scale is minor, with a minor third.