An interval is the distance between two notes. It is labeled by its numerical value and its quality.
- The numerical value indicates the number of steps the higher note is from the lower one. For example E is the 3rd of C because E is three steps (C, D, E) away from C.
- The quality of any interval is labeled using the terms Perfect (P), Major (M), Minor (m), Augmented (A), and diminished (d).
In a major scale the intervals are as follows:
1st (unison): Perfect
- If a Major interval is lowered by half a step, its quality changes to Minor. For example, C to D is a Major 2nd (M2), but C to Db is a Minor 2nd (m2). If a Major interval is raised by half a step, its quality changes to Augmented. For example, C to D# is an Augmented 2nd (A2).
- If a Perfect interval is lowered by half a step, its quality changes to Diminished. For example, C to G is a Perfect 5th (P5), but C to Gb is a Diminished 5th (d5). If a Perfect interval is raised by half a step, its quality changes to Augmeneted. For example, C to G# is an Augmented 5th (A5).
An interval may be described as harmonic or melodic. A melodic interval refers to successively sounding notes, such as two adjacent notes in a melody. A harmonic interval refers to two simultaneously sounding tones.