In one sense, the diminished triad is in the same league as the major and minor triads, since it also occurs within the notes of the major scale. However, it is used a great deal less often, and when it is used it’s frequently employed as a transitional chord, often arising out of half-step motion, especially in the movement I-#i dim-ii or IV-#iv dim-V in major—a sound heard frequently in American gospel music and in music like R&B that takes gospel influence. It also appears once in the major scale as the triad based on the seventh scale degree. When it appears in this context it can often feel like a dominant seventh (V7) chord with a missing root.
The Diminished Triad
Symbols & Abbreviations:
Diatonic, Melodic Minor, Octatonic