What happens to the 6th note in the melodic form of minor scales on the way up?

In the context of melodic minor scales, the 6th note is raised a semitone when ascending. This alteration serves to create a more fluid melodic line and contributes to the overall musical expression in minor keys. The specific adjustment to the 6th note, raising it from a flat 6th to a natural 6th, helps to generate stronger melodic movement and emphasizes the leading tone, which is especially important for resolving to the tonic.

This alteration contrasts with the natural minor scale, where the 6th note remains unchanged, and it does not apply the same way on the way down, where the 6th resolves back to its original form. The choice to raise the 6th note while ascending can enhance the melodic function of the scale, which is particularly useful in compositions that require a more vibrant and uplifting feel.

Other options do not align with the established rules of melodic minor scales in music theory, as they either propose changes that do not occur or suggest characteristics that apply to different contexts within scale construction.