Odim and udim

Odim and udim are a pair of inversely related chords of 7-limit just intonation, 1-6/5-7/5 and 1-7/6-7/5 in any position and voicing, and may also be called the major and minor Huyghens triads.. They belong to a rank three subgroup of the 7-limit, 2.5/3.7/3, and in some ways are analogous to the major and minor 5-limit triads, which also belong to a rank-three subgroup of the 7-limit. Analogous to zarlino, the 5-limit "JI diatonic", is the tritriadic scale 6/5-7/5-10/7-42/25-12/7-49/25-2, and analogous to meantone is starlingtet.