The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped.
Bb69 is Bb, D, F, G and C — Bb6 with the ninth added as well.
It sounds wide and entirely at rest. The modern way to voice a tonic when a triad is too bare and a maj7 too pointed.

| Bb | D | F | G | C |
|---|---|---|---|---|
| 1 | 3 | 5 | 6 | 9 |
Tonic — it commits to nothing.
Also written Bb6/9, Bb6add9 or Bb six nine. The same chord either way; which spelling you meet depends on who wrote the chart.
The same operation one voice further down: the third voice from the top falls an octave and becomes the bass.
That leaves a bigger hole under the top three notes, so a string gets skipped: the muted string in the middle is the shape, not a mistake.
Bb69 has 10 of them, on strings 6-4-3-2 and strings 5-3-2-1, from open position up to the 15th — every inversion the chord has: Bb in the bass, D in the bass, G in the bass and C in the bass. The one to learn first is the G shape at the nut.
5 of them sit on strings 6-4-3-2, so you can run the inversions up one set without changing strings — which is the whole reason to learn them as a family rather than as separate grips.
Start with x-13-10-12-11-10 — no barre. 1 of the 8 shapes here sits in open position. 7 of the 8 need a barre. Together they cover the neck from the 1st fret to the 13th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x10011 | open position | Bb, root position | F | barred |
| x33333 | 3rd fret | C, 9th in the bass | G | barred |
| 655566 | 5th fret | Bb, root position | Bb | barred |
| xx8788 | 7th fret | Bb, root position | C | barred |
| x88788 | 7th fret | F, 2nd inversion | C | barred |
| x-10-10-10-11-10 | 10th fret | G, 6th in the bass | D | barred |
| x-13-10-12-11-10 | 10th fret | Bb, root position | D | all fretted |
| x-13-12-12-13-13 | 12th fret | Bb, root position | F | barred |
The same notes rebuilt from scratch give 5 shell, 15 drop 2, 15 rootless and 4 open string voicings, each on its own page.
Tensions. A shell of Bb69, root, third and seventh, leaves a string free, and the tones that belong over it are the #11 (E).
How you get to it. The turn that lands on Bb69 is Cm7 to F7 — the ii and the V of Bb — and F7 shares its third and seventh with Cm7, so the hand barely moves between them.
In which keys. Every note of Bb69 belongs to C minor (the ♭VII), D minor (the ♭VI), Eb major (the V), F major (the IV), G minor (the ♭III) and Bb major (the I).
Bb69 is every note of the Bb major pentatonic, and nothing else. It also sits inside Bb major, Bb lydian, Bb mixolydian and Bb lydian dominant.
Change one note of Bb69 and you have Bbmaj9 (the sixth becomes a major seventh), Bbmaj13 (add the major seventh), Bbm69 (the major third becomes a minor third), Bbadd9 (drop the sixth), Bb6 (drop the ninth) or Bb9 (the sixth becomes a flat seventh).
Bb69 is a major chord — root, major third, fifth. Major chords on every root.
On Bb69’s sound and use this page follows Mark Levine, The Jazz Piano Book (Sher Music, 1989). The shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.