Bb sixth/ninth chord
Bb6/9 chord for piano with keyboard diagram.
Explanation: The B flat sixth/ninth is a five note chord. Due to practical circumstances, however, the fifth (F) is often omitted and/or the chord is played inverted. The chord is abbreviated Bb6/9.
Theory: The Bb6/9 chord is constructed with a root, a major third, a perfect fifth, a major sixth and a major ninth.
Notes: Bb - D - F - G - C