Fb13 chord

The F-flat dominant thirteenth chord (abbreviated "Fb13 chord") is a seven-note chord consisting of the notes F♭, A♭, C♭, E♭♭, G♭, B♭♭, and D♭. The chord is formed by adding a thirteenth to a F-flat dominant eleventh chord.

In practice, the fifth (C♭) and eleventh (B♭♭) are often omitted from the Fb13 chord to avoid a very dissonant sound, and because it's not always possible to play all notes simultaneously.