Minor Tonality and Voice-Leading Choices

Core Idea

Minor keys present voice-leading choices between harmonic minor (which provides the major V chord via raised 7) and melodic minor (which raises both 6 and 7 in ascending passages). These choices affect voice-leading fluency and harmonic color.

Explainer

From your prerequisite study of the harmonic and melodic minor scales, you know that minor keys are not a single fixed scale but a flexible tonal resource that exists in several forms. The harmonic minor raises scale degree 7 to create a leading tone; the melodic minor additionally raises scale degree 6 when ascending to avoid the awkward augmented second between 6 and the raised 7; and the natural minor uses neither alteration. In four-part harmony, each voice may need a different form of the scale at any given moment, and choosing which form to use is one of the defining practical challenges of minor-key writing.

The central principle is function-driven scale selection. The raised seventh (the leading tone) is required whenever the dominant chord must function as a major triad — without it, the V chord becomes a minor triad lacking the leading tone's half-step pull to the tonic, and the cadential force is drastically weakened. In any voice that forms the third of a V chord, or that moves upward by half-step to the tonic, harmonic minor is required. This is not optional coloring; it is a structural necessity. In A minor, the note G♯ must appear in the tenor or soprano when spelling the E major (V) chord, regardless of what form the scale "normally" uses.

The choice between natural and melodic minor becomes more nuanced in upper voices. When an upper voice ascends stepwise through scale degrees 6 and 7 toward the tonic (la-ti-do), the melodic minor is preferred — raising both 6 and 7 avoids the augmented second (the interval F–G♯ in A minor) that creates an angular, difficult-to-sing leap. When a voice descends through that same territory, both alterations are dropped: descending, the natural minor's lower sixth and seventh give the line a flatter, darker character. This asymmetry — ascending melodic minor, descending natural minor — is one of the defining patterns of tonal minor voice leading.

A useful mental model: before writing any note in a minor-key passage, ask two questions about that voice. First, does it need the leading tone (raised 7) because it is ascending to the tonic by half-step, or because it forms the third of a dominant chord? If yes, raise it. Second, is it ascending stepwise through scale degrees 5–6–7–8? If yes, use melodic minor (raise both 6 and 7) to avoid the augmented second. These two questions cover the vast majority of minor-key decisions. The remaining cases — leaping motion, non-dominant harmonies, deliberately modal passages — can be handled by ear once the default rules are internalized. The underlying goal is always voice-leading fluency: each voice should move smoothly, with no awkward intervals, while supporting the harmonic function of each chord.