MusicScale[TemperedChromatic, freq, dur] creates a Sound object that is a sequence of pitches corresponding to an equal-tempered scale.
TemperedChromatic gives a list of intervals in which the octave is divided into 12 equal parts.
Each part is a tempered semitone (100 cents).
This is equivalent to making 12 fifths equal to 7 octaves, so an equal-tempered fifth is equal to 700 cents. (The Just Intonation and Pythagorean fifths are 702 cents, and the Mean Tone fifth is 696.6 cents.)
This process guarantees equivalence between pitches, and allows intervals to be the same in all keys.
However, except for the octave, none of the intervals is in tune with regard to mathematical ratios and the logic Pythagoras developed from proportional lengths of strings.