Intervals

An interval describes the distance between two notes. The distance from any note to its nearest neighbor is a semitone; two semitones make a tone, sometimes called a whole tone (see the page on pitch for examples of these). However, when we need to describe larger distances it is generally not practical to describe them in terms of tones and semitones, so there is a way of describing intervals which indicates not only the distance between the notes, but also converys information about the harmonic context in which they occur. Therefore the full classification of an interval has two parts - number and quality.

Number is figured out by simply counting the lines and spaces between and including the two notes of the interval; so the interval from C to D is a second, the interval from C to E is a third, and so on. (The interval from C to the next C above it is called an octave, not an eighth.) The quality of an interval is either major, minor, perfect, diminished or augmented. (Doubly-diminished and doubly-augmented, or trebly-diminished and trebly-augmented intervals are possible, but unusual.) Using the C major scale, the major intervals are the 2nd, 3rd, 6th and 7th from the key-note (tonic), i.e. from C up to D is a major second, C-E is a major 3rd, C-A is a major 6th, and C-B is a major 7th. The remaining intervals are perfect, i.e. C up to F is a perfect 4th, C-G is a perfect 5th, and C-C is a perfect octave (8ve). The other qualities are formed according to the following rules:

When either the upper note of a major interval is raised a semitone (with an accidental), or the bottom note lowered a semitone (with an accidental), the resulting interval is augmented.
When either the upper note of a major interval is lowered a semitone (with an accidental), or the bottom note raised a semitone (with an accidental), the resulting interval is minor.
When either the upper note of a minor interval is lowered a semitone (with an accidental), or the bottom note raised a semitone (with an accidental), the resulting interval is diminished.
When either the upper note of a perfect interval is raised a semitone (with an accidental), or the bottom note lowered a semitone (with an accidental), the resulting interval is augmented.
When either the upper note of a perfect interval is lowered a semitone (with an accidental), or the bottom note raised a semitone (with an accidental), the resulting interval is diminished.

For example, the interval from C up to E is a major 3rd; lower the E to E flat (i.e. make the interval a semitone smaller) and the interval between the two notes (C up to E flat) is a minor 3rd. Again, C up to E is a major 3rd; lower the C to C flat (i.e. make the interval a semitone larger) and the interval between the two notes (C flat up to E) is an augmented 3rd. C up to E flat is a minor 3rd; raise the C to C sharp (i.e. make the interval a semitone smaller) and the interval between the two notes (C sharp up to E flat) is a diminished 3rd.

It is possible in some circumstances to refer to intervals with much less specificity. For example, both major and minor seconds may be referred to as a step. Intervals greater than a second may be referred to as a skip, jump, or leap. We may also describe intervals as being either melodic or harmonic. A melodic interval occurs when the notes follow each other, a harmonic interval occurs when the notes sound at the same time.

An Interval Test

If your browser is Java enabled, you can use the applet to test your skill at naming intervals. When you press the 'New Interval' button the applet will display two notes: the lower one will be a random pitch between C flat and B sharp inclusive; the upper note will be a random pitch between D flat and A sharp inclusive. These notes will also be displayed as text in the boxes. Pressing the 'Show Answer' button will display the interval's name in the 'answer' box.

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