B7#9 guitar chord
The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped.
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About B7#9 — drop 3 voicings
B7#9 is B, D#, F#, A and D — B9 with the ninth raised a semitone.
It sounds gritty and contradictory. The minor third sounding over the major third; every guitarist knows it as the Hendrix chord.
B7#9 notes and formula
| B | D# | F# | A | D |
|---|---|---|---|---|
| 1 | 3 | 5 | ♭7 | ♯9 |
Altered dominant — dominant function with a blues third on top.
Also written B7(#9), B7+9 or B7♯9. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play B7#9
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.
B7#9 has 8 of them, on strings 6-4-3-2 and strings 5-3-2-1, from open position up to the 11th — every inversion the chord has: B in the bass, D# in the bass, A in the bass and C## in the bass. The one to learn first is the A shape at the nut.
4 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 x2123x — no barre and down at the nut. None of the shapes for B7#9 uses an open string, so every one of them is movable; the lowest sits at the 1st fret. 4 of the 10 need a barre. Together they cover the neck from the 1st fret to the 15th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x2123x | 1st fret | B, root position | D | all fretted |
| x54445 | 4th fret | C##, 9th in the bass | A | barred |
| 760705 | 5th fret | B, root position | A | 2 open strings |
| 7677xx | 6th fret | B, root position | D | barred |
| x67777 | 6th fret | D#, 1st inversion | B | barred |
| 7-9-7-8-10-10 | 7th fret | B, root position | D | all fretted |
| 7-9-7-8-7-10 | 7th fret | B, root position | D | barred |
| x-x-9-8-10-10 | 8th fret | B, root position | D | all fretted |
| x-9-9-8-10-10 | 8th fret | F#, 2nd inversion | D | all fretted |
| x-14-13-14-15-x | 13th fret | B, root position | D | all fretted |
The same notes rebuilt from scratch give 4 shell, 13 drop 2, 13 rootless and 5 open string voicings, each on its own page.
Tensions. A shell of B7#9, root, third and seventh, leaves a string free, and the tones that belong over it are the #11 (E#), the b13 (G) and the 13 (G#).
How to use B7#9
B7#9 is a dominant with its tension raised, so it still points at E — harder than a plain seventh does, because the altered tones sit a semitone from where they are going.
Voice by voice, B7#9 → E. 2 voices move by a semitone, and one note is common to both chords.
| In B7#9 | Moves | In E |
|---|---|---|
| B, the root | stays where it is | B, the fifth |
| D#, the major third | rises a semitone | E, the root |
| F#, the fifth | falls a whole tone | E, the root |
| A, the flat seventh | falls a semitone | G#, the major third |
| D, the sharp ninth | rises a whole tone | E, the root |
What to play over B7#9
Every note of B7#9 is in B half-whole diminished.
Chords near B7#9
Change one note of B7#9 and you have Bm7 (drop the major third), Bm9 (the major third becomes a ninth), B7 (drop the minor third), B9 (the minor third becomes a ninth) or B7b9 (the minor third becomes a flat ninth).
B7#9 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On B7#9’s sound and use this page follows Mark Levine, The Jazz Theory Book (Sher Music, 1995). The shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.