The following section is intended to introduce the student to basic harmony (defined as any simultaneous combination of sounds) via the recognition of common intervals. An interval is defined as the distance between two musical notes, (or degrees of a scale). Intervals are measured from the lower note upwards to the higher note.
Number and type names of intervals are used, i.e. a 3rd can be major or minor, depending upon the distance from one note to the next.
There are five basic types of intervals which are listed below.
Perfect intervals are 4ths, 5ths and octaves. If you widen any of these intervals by a semitone they become augmented and if you narrow them by a semitone they become diminished. Major intervals become minor if narrowed by a semitone and minor intervals become major if widened by a semitone. Examples of intervals which can be major or minor are 2nds, 3rds, 6ths and 7ths. An augmented interval can be created by widening a perfect or major interval by a semitone. A diminished interval can be created by narrowing a perfect or minor interval by a semitone.
For the purpose of demonstration, the difference between a major and minor 3rd is described below.
To change to a minor 3rd, lower the upper notes of the above intervals by one half tone (the minor 3rd is half a tone less than the major 3rd).