About the Ddim chord
To play D diminished, use the first shape above. Use your index finger to barre the 1st fret across the G, C, and E strings. Place your middle finger on the 2nd fret of the C string and your pinky finger on the 5th fret of the A string. Strum all four strings and check that each one rings cleanly.
Root
D
Quality
Diminished
Notes
D · F · Ab
How the Ddim chord works
D
Root(1)
The home note. It gives the chord its name.
F
Minor third(♭3)
The defining minor interval above the root.
Ab
Diminished fifth(♭5)
A lowered fifth that adds harmonic tension.