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
Pitch interval Thus the ordered pitch class interval, i<"x", "y">, may be defined as: Ascending intervals are indicated by a positive value, and descending intervals by a negative one. Pitch interval In musical set theory, a pitch interval (PI or ip) is the number of semitones that separates one pitch from another, upward or downward. They are notated as follows: For example C4 to D4 is 3 semitones: While C4 to D5 is 15 semitones: However, under octave equivalence these are the same pitches (D4 & D5, ), thus the #Pitch-interval class may be used. In musical set theory, a pitch-interval class