Bb Eleventh chord (Bb11) on the guitar fretboard

The Bb Eleventh chord (Bb11) is made of Bb (the root), D (major third, optional), F (perfect fifth), Ab (minor seventh), C (major ninth, optional) and Eb (perfect eleventh). The fretboard shows every one of them across the neck in standard tuning (E A D G B E), and plays them back so you can hear the chord.

The eleventh chord extends a dominant ninth to the eleventh, and the map marks the third, ninth and others as optional. In practice many of its notes can be left out, so shapes on the neck range from sparse to full. It sits between the ninth and the thirteenth.