What alteration is made to the 7th note in the harmonic form of minor scales?

In the harmonic form of minor scales, the 7th note is raised a semi-tone compared to the natural minor scale. This alteration is essential for creating a leading tone, which is the note that leads into the tonic or the first note of the scale. The raised 7th enhances the harmonic tension and resolves more strongly to the tonic, providing a stronger sense of resolution.

In a natural minor scale, the 7th note is a whole step below the tonic, which can result in a less pronounced resolution. By raising the 7th note, composers and musicians can achieve a more dramatic and effective sound in their music, particularly in the context of Western classical music. This is why raising the 7th a semi-tone is a defining characteristic of the harmonic minor scale.