About the D7 chord
To play D dominant 7th, use the first shape above. Use your index finger to barre the 2nd fret across the G, C, and E strings. Place your middle finger on the 3rd fret of the A string. Strum all four strings and check that each one rings cleanly.
Root
D
Quality
Dominant 7th
Notes
D · F# · A · C
How the D7 chord works
D
Root(1)
The home note. It gives the chord its name.
F#
Major third(3)
The major-third interval that establishes the chord's major base.
A
Perfect fifth(5)
Adds strength and stability.
C
Minor seventh(♭7)
Adds the defining minor-seventh color.