Intervals

Notice that 4th's, 5'ths, 1's, and 8ve's are never major or minor. They can
only be perfect, augmented or diminished.

When intervals are altered, their quality changes.
If a major or perfect interval is increased in size by one half step it becomes augmented.
If a major interval is decreased in size by one half step, it becomes minor.
If a minor or perfect.interval is decreased in size by one half step,
it becomes diminished.

The following chart shows the relationships between interval qualities.
Each space between interval quality represents a change of a half step.

For seconds, thirds, sixths and sevenths:

From left to right, interval is increasing in size by one half step.
diminshed-----minor------major------augmented

For fourths, fifths, unisons, and octaves:

From left to right, interval is increasing in size by one half step.
diminished-----perfect------augmented

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