High Quality Content by WIKIPEDIA articles! In music, 31 equal temperament, 31-ET, which can also be abbreviated 31-TET, 31-EDO (equal division of the octave), also known as tricesimoprimal, is the tempered scale derived by dividing the octave into 31 equal-sized steps (equal frequency ratios). Play (help·info) Each step represents a frequency ratio of 21/31, or 38.71 cents ( Play (help·info)).