ABSTRACT
Combining two pitches together forms an interval. Intervals are the elemental building blocks of scales, melodies, and chords. The notes of a harmonic interval occur at the same time, while those of a melodic interval sound consecutively. Intervals are either consonant or dissonant. Dissonant intervals sound harsh and tend to resolve to consonant ones. An interval is labeled based on its size and quality. Perfect consonances, the most stable class of intervals, include the perfect unison, perfect fourth, perfect fifth, and perfect octave. Imperfect consonances include thirds and sixths, which can be major or minor. Dissonances include seconds, sevenths, and all augmented or diminished intervals, including the tritone. To invert an interval, swap the position of its notes, either by moving the upper note down one octave or by shifting the lower note up an octave. The intervals expand by one half step from left to right.
