About the Edim chord
To play E diminished, use the first shape above. Place your index finger on the 1st fret of the A string and your pinky finger on the 4th fret of the C string. Leave the G and E strings open. Strum all four strings and check that each one rings cleanly.
Root
E
Quality
Diminished
Notes
E · G · Bb
How the Edim chord works
E
Root(1)
The home note. It gives the chord its name.
G
Minor third(♭3)
The defining minor interval above the root.
Bb
Diminished fifth(♭5)
A lowered fifth that adds harmonic tension.