Watch the Power Chords online guitar lesson by Matthieu Brandt from Chord Cookbook
A diminished 7th chord is a diminished triad (1-b3-b5) with a diminished seventh added. This note is a flatted flatted seventh, or double flatted seventh. Its most common use is in bar six of a Jazz Blues, but some pop songs like 'Michelle' by the Beatles also use it. Powerchords are often seen in heavy metal and hard rock. The 'chord' consists of two notes; the root and the perfect fifth.