What is a diminished interval?

A diminished interval is defined as a perfect or major interval that has been reduced by a half step. In terms of music theory, this means that when you take a perfect interval—such as a perfect fifth—and lower it by a half step, it becomes diminished. Similarly, if you take a major interval, such as a major third, and lower it by a half step, it also becomes diminished.

This concept is essential in understanding harmony and chord structures in music. The idea of diminishing an interval is crucial for forming specific chords, particularly diminished chords, which have a unique sound and are prevalent in various musical genres. By recognizing that a diminished interval stems from modifying the existing perfect or major intervals, you gain a deeper insight into how intervals function within music.

In contrast, raising or lowering intervals without this specific half-step alteration won't yield a diminished interval. Thus, knowing that a diminished interval emerges from a perfect interval lowered by a half step helps delineate the structure and classification of musical intervals.