Text: The Perfect Interval is a Major Interval where the lower tone is found in the Major Scale of the upper tone as well as the upper tone is found in the Major Scale of the lower tone. The Major 6th to the right is Major as D is part of the Major Scale of F but F is not part of the Major Scale of D. Therefore it is not a Perfect Interval. The Perfect 4th to the lower right is Perfect because F is found in the Major Scale of C and C is found in the Major Scale of F. Perfect Intervals may be a 1st, 4th, 5th and 8th.

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