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In music, the interval between the key note (tonic) and a higher note from the same major scale. Seconds, thirds, sixths, and sevenths can all be major (or minor) intervals, but fourths, fifths, and octaves are called perfect intervals, in both major and minor keys. If the upper note of the major interval is flattened (or the lower note is sharpened) it becomes a minor interval. If the upper note of a major interval is sharpened (or the lower note is flattened) it becomes an augmented interval. If the upper note of a minor seventh is flattened (or the lower note is sharpened) it becomes a diminished seventh (which is equivalent to a major sixth).
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