"dim7", or "o7" for short, but often just called "dim", because the triad is so rare Found on vii degree of harmonic minor only Common vii chord in minor key, sometimes used as sub for the V, or as a chromatic passing chord in major or minor keys (Often but not always interpreted as a sub for a dom7 rooted a halfstep below)The dim triad is built with the formula 1b3b5 The dim 7th is built with the formula 1b3b5bb7 Notice that the dim7 chords are symmetrical All inversions of the The first chord progression below contains a normal 7th chord In the second progression the 7th chord has been substituted with a dim7 chord Diminished 7 Chord Substitution Play both progressions to hear the sound of the substitution;
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