Natural minor (Aeolian) is the “darker / melancholic” counterpart to major. It’s the relative minor of a major key (same notes, different tonic), which is why modulating between relative major/minor feels so natural. Common genres: rock, pop ballads, classical, cinematic, indie. Usage: great for i–bVII–bVI progressions (a classic minor-key sound), and for melodies that lean on the b3, b6, and b7. Harmonically it lacks a strong leading tone (7→1), so cadences can feel modal unless you introduce harmonic/melodic minor.