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Interval Qualities
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Chapter 3 · Lesson 02
Two intervals of the same size are not always equal. How many tones and semitones an interval spans determines its quality: minor, major, perfect, augmented or diminished.
Lesson Notes
In the previous lesson we learned to find the size of an interval, its number. But two intervals of the same size may not be exactly equal. That is where the interval's second characteristic comes in, its quality.
01Same size, different sound
Compare two seconds: from C to D, and from E to F. Both are seconds, two neighbouring note names. But they are not equal. C-D spans a tone, while E-F spans only a semitone.
02The five qualities
There are five interval qualities, each with its own abbreviation: minor (m), major (M), perfect (P), augmented (A) and diminished (d).
Each size, though, takes only certain qualities. Seconds, thirds, sixths and sevenths are minor or major, one semitone apart. Unisons, fourths, fifths and octaves don't split into minor and major. They have only one natural form, which is why they are called perfect.
03How many tones each one spans
The table below shows every quality with its tones and an example, all starting from C. Notice the pattern: the minor interval is always one semitone below the major one.
04Augmented and diminished
The last two qualities describe intervals that are slightly larger or slightly smaller than usual. When a perfect or major interval grows by one semitone, it is called augmented (A). When a perfect or minor interval shrinks by one semitone, it is called diminished (d). This applies to an interval of any size, and it can come from accidentals or even from natural notes.
05Enharmonic intervals
Look again at the two intervals in the figure above. C-F♯ (A4) and C-G♭ (d5) both span 3 tones, so they sound identical. But they are written differently and have different names. Two intervals with the same sound but different spelling are called enharmonic.
Recap
- The quality says exactly how large an interval is: minor (m), major (M), perfect (P), augmented (A), diminished (d).
- Seconds, thirds, sixths and sevenths are minor or major. Unisons, fourths, fifths and octaves are perfect.
- The difference between minor and major is one semitone.
- Perfect or major + semitone = augmented. Perfect or minor − semitone = diminished.
- Example from C: C-F♯ = augmented 4th, C-G♭ = diminished 5th.
- Two intervals with the same sound but different spelling are called enharmonic (C-F♯ and C-G♭).
Keep learning with your teacher
Bring what you have been practicing to your next lesson. We can work on the sound, technique and musical questions together.
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