The G-flat dominant seventh chord (abbreviated "Gb7 chord") is a four-note chord consisting of the notes G♭, B♭, D♭, and F♭. The chord is formed by adding a minor seventh to a G-flat major chord.
G-flat dominant seventh chord
G-flat major-minor seventh chord
G♭ B♭ D♭ F♭
1 3 5 ♭7
tetrad (four-note chord)