Which mode is associated with the interval alteration flat 3 and flat 7?

Which mode is associated with the interval alteration flat 3 and flat 7?

• A. Dorian
• B. Phrygian
• C. Ionian mode
• D. Lydian

Answer: (C)

Recognizing the mode with flat 3 and flat 7 means looking for both the third and the seventh degrees lowered by a half step relative to the major scale. The Dorian mode does exactly this: it lowers the third and the seventh while keeping the other degrees as in the major scale on the same tonic, giving a minor triad with a natural sixth. To see it in action, take the major scale built on C and start on its second degree to form the Dorian mode: D E F G A B C. Compare the intervals above the tonic D with a D major reference (D E F# G A B C#). The third above D is F instead of F#, and the seventh above D is C instead of C#. That’s flat 3 and flat 7, which defines Dorian. Ionian (the major mode) would have both the third and the seventh natural, not lowered. Lydian alters a different degree (raised fourth), and Phrygian involves additional changes such as a flattened second along with other alterations. So the combination of flat 3 and flat 7 points to the Dorian mode.

Recognizing the mode with flat 3 and flat 7 means looking for both the third and the seventh degrees lowered by a half step relative to the major scale. The Dorian mode does exactly this: it lowers the third and the seventh while keeping the other degrees as in the major scale on the same tonic, giving a minor triad with a natural sixth.

To see it in action, take the major scale built on C and start on its second degree to form the Dorian mode: D E F G A B C. Compare the intervals above the tonic D with a D major reference (D E F# G A B C#). The third above D is F instead of F#, and the seventh above D is C instead of C#. That’s flat 3 and flat 7, which defines Dorian.

Ionian (the major mode) would have both the third and the seventh natural, not lowered. Lydian alters a different degree (raised fourth), and Phrygian involves additional changes such as a flattened second along with other alterations. So the combination of flat 3 and flat 7 points to the Dorian mode.