Bb Ninth chord (Bb9) on the guitar fretboard

The Bb Ninth chord (Bb9) is made of Bb (the root), D (major third), F (perfect fifth, optional), Ab (minor seventh) and C (major ninth). 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 ninth chord is a dominant seventh with a ninth stacked above it, five notes in its full form. The fifth is optional, so many neck shapes leave it out. Its nearest relatives are the dominant seventh below it and the eleventh and thirteenth above.