Defining Quality
In music of the West where the octave is divided into twelve equal semitones, the interval numbers of the unison
(1) to the octave (8) may be further defined by five qualities:
- Perfect
- Major
- Minor
- Diminished
- Augmented
The quality of an interval may be determined in two ways: (1) by relating the interval to a major scale; or (2) by
counting the number of half steps between the two pitches forming the interval. Your instructor may have a
preference; use the method that is assigned to determine the interval number and quality.
Intervals of the Major Scale: Perfect and Major
Method 1: Using the major scale to determine perfect and major intervals
Intervals formed from the tonic pitch up to each note of a major scale are either perfect or major.
- Perfect intervalsare 1, 4, 5, 8.
- Major intervalsare 2, 3, 6, 7.
- Use the diagram to help you visualize this. (Note: the overlapping section of the circles will be discussed
later in this module.)
For example, let’s look at the A major scale with three sharps in its key signature.
The quality for intervals 1, 4, 5, 8 is perfect(abbreviated to “P”). These intervals may also be expressed as a
ratio of sound frequencies of 1:1, 4:3, 3:2, and 2:1, respectively. (See Appendix 2 for a further discussion on
acoustics and sound frequencies.)
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Perfect Major1 4 5 8 2 3 6 7MODULE 10