Music Theory

Lesson 11


Interval Size and Quality Review


Before moving on to new material, I would like to quickly review what we learned in the last lesson.  An interval is the distance between two pitches.  Intervals can be harmonic (simultaneous) or melodic (successive).  There are two identifying features of every interval: size and quality.  Interval size is identified by an ordinal number, or the number of pitch names needed to count from one pitch to the other. Interval quality is based on the number of semitones an interval contains; a simple way to calculate this information relates to the intervals found in the major scale.  The unison, fourth, fifth, and octave in the major scale are called perfect intervals, while the second, third, sixth and seventh are called major.  If the perfect intervals are lowered by a chromatic semitone, they become diminished, and if they are raised by a chromatic semitone they become augmented.  If the major intervals are raised by a chromatic semitone, they become augmented.  If they are lowered by a chromatic semitone, they become minor, and if they are lowered by two chromatic semitones, they become diminished.  This information is summarized by the following chart:







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Mark McFarland