Scientific pitch notation creates a linear pitch space in which an octave spans 12 semitones, where each semitone is the distance between adjacent keys of the piano keyboard. Distance in this space corresponds to musical pitch distance in an equal-tempered scale; 2 semitones being a whole step, 1 semitone being a half step. An equal-tempered semitone can also be subdivided further into 100 cents. Each cent is semitone or octave. This measure of pitch allows the expression of "microtones" not found on standard piano keyboards. The notation is sometimes used in the context of meantone temperament, and does not always assume equal temperament
Rule of the octave Rule of the octave The rule of the octave is a way of harmonizing each note of the diatonic scale, reflecting common practice, and has its origin in the practice of thorough bass, or basso continuo. The rule of the octave also formed the cornerstone of the "regole" (rules) of partimento collections. The rule of the octave was first mentioned in the 17th century in treatises for thorough bass written for lute-like instruments. There is normally a different harmonization for ascending and descending bass lines, and, although called a rule, there are several variants with different chords. Different versions for