Diminished 7th Chords

In most sheet music books, Cdim or C° denotes a diminished seventh chord with root C.  Some modern jazz books and some music theory literature use  Cdim or C°  to denotes  diminished  chord, while Cdim7 or C°7 denotes a diminished seventh chord.

A diminished 7th chord is comprised of a diminished triad ( is a triad consisting of two minor thirds above the root) plus a double flattend 7th (same note as the 6th). It’s primary use is  to lead to the tonic, or root note of the song.

Here are a few ways to play a diminished 7th chord.