Bb9 guitar chord — root mapping, fingerings, arpeggios, triads, pentatonic, scales

Lydian Dominant is a major mode with #4 and b7, the fourth mode of melodic minor. Over a dominant 7th chord, #4 functions as #11, making the scale a natural choice for 7#11 and 13#11 without an altered 9th. It is used on tritone substitutions, secondary dominants, backdoor dominants and non-functional I7 chords when a bright dominant sound is required without a natural 11th.

Lydian Dominant is a major mode with a raised 4th and lowered 7th degree. It combines the Lydian #4 with the Mixolydian b7: the major 3rd preserves its major quality, b7 produces a dominant seventh chord on the tonic, and #4 adds the defining #11. The mode contains two tritones: one between 1 and #4, and another between 3 and b7. Its tonic seventh chord is I7, with I7#11 as its characteristic extended form. Its defining degrees are #4 and b7.

1 — tonic / chord root: the modal center and the root of the major I triad and dominant seventh chord I7.

2 — major 2nd / 9th: the root of the major II chord; over I7 it functions as a natural 9.

3 — major 3rd: establishes the mode’s major quality, belongs to I7, forms a tritone with b7, and serves as the root of the diminished iii° chord.

#4 — augmented 4th / sharp 11th: the primary defining degree of the mode. It functions as the #11 over I7, forms a tritone with the tonic, belongs to II7 as its major 3rd, and serves as the root of the diminished #iv° chord.

5 — perfect 5th: a stable tone of I7 and the root of the minor v chord. Degree #4 lies a semitone below it and may move upward to 5.

6 — major 6th / 13th: functions as a natural 13 over I7 and serves as the root of the minor vi chord.

b7—minor 7th / subtonic: belongs to I7, forms a tritone with the major 3rd 3, and serves as the root of the augmented bVII+ chord. It lies a whole tone below the tonic and does not function as a conventional leading tone.

Harmonizing the scale in triads produces:

I—major; II — major; iii° — diminished; #iv° — diminished; v — minor; vi — minor; bVII+ — augmented.

The diatonic seventh chords are I7, II7, iiiø7, #ivø7, v(maj7), vi7, and bVIImaj7#5.

The principal harmonic marker is the dominant seventh tonic chord I7 with an available #11. The natural 2 and 6 add the 9 and 13, so its complete characteristic extension set can be represented as 13#11.

Both I7 and II7 have dominant seventh quality. Their function depends on context: I7 may act as an independent center, a non-resolving dominant chord, or a tritone substitute for another dominant. The two adjacent diminished triads, iii° and #iv°, together with the minor-major seventh chord v(maj7), distinguish this harmonization from those of the ordinary diatonic modes.

In C Lydian Dominant, the triads are C D Edim F#dim Gm Am Bbaug; the seventh chords are C7 D7 Em7b5 F#m7b5 Gm(maj7) Am7 Bbmaj7#5.

In jazz chord-scale theory, Lydian Dominant is used primarily over dominant seventh chords with a raised 11th: 7#11, 9#11, and 13#11. Degrees 1 3 5 b7 match the dominant seventh chord tones, while 2, #4, and 6 supply the natural 9, #11, and 13. For example, C Lydian Dominant is used over C7#11.

The mode is especially characteristic over dominant chords that do not resolve through an ordinary V7–I motion, but instead function as independent colors, static harmonies, or parts of progressions with nonstandard resolutions. When the melody or chord symbol explicitly contains a #11, Lydian Dominant represents the harmony more accurately than ordinary Mixolydian.

Another important application is the tritone substitution. In the progression Dm7–Db7#11–Cmaj7, for example, Db7 replaces G7, and Db Lydian Dominant may be used over it. Its major 3rd and minor 7th correspond to the essential guide tones of the substituted dominant, while the chord root resolves downward by semitone.

The mode is not a universal choice for every 7 chord. A natural 11 conflicts with its #11, while chords requiring b9, #9, or b13 call for a different dominant scale. Over an ordinary unaltered V7 without a raised 11th, Mixolydian generally remains the more standard choice.

Lydian Dominant is the fourth mode of Melodic Minor. Its relative parent Melodic Minor scale begins a perfect 5th above its tonic. For example, C Lydian Dominant and G Melodic Minor contain the same notes, C D E F# G A Bb, but C is the center in the former and G in the latter.

Its closest parallel mode is Mixolydian, 1 2 3 4 5 6 b7. It differs only in the 4th degree: Lydian Dominant uses #4. Ordinary Lydian has the formula 1 2 3 #4 5 6 7 and uses a major 7th instead of b7. Lydian Dominant can therefore be understood as Lydian b7 or Mixolydian #4. It is also called the Acoustic Scale, although terminology varies between theoretical systems.

The mode is closely related to the Altered Scale rooted a tritone away. For example, C Lydian Dominant and F# Altered contain the same pitch collection—the notes of G Melodic Minor. This relationship explains its use over tritone-substitute dominant chords.

The seven modes of Melodic Minor are:

1 — Melodic Minor: 1 2 b3 4 5 6 7;

2 — Dorian b2: 1 b2 b3 4 5 6 b7;

3 — Lydian Augmented: 1 2 3 #4 #5 6 7;

4 — Lydian Dominant: 1 2 3 #4 5 6 b7;

5 — Mixolydian b6: 1 2 3 4 5 b6 b7;

6 — Locrian ♮2: 1 2 b3 4 b5 b6 b7;

7 — Altered, or Super Locrian: 1 b2 b3 b4 b5 b6 b7.

Over 7#11, begin with the dominant seventh chord tones 1 3 5 b7. The major 3rd and minor 7th form a tritone and identify the chord quality most clearly. To make the line sound specifically Lydian Dominant, emphasize #4: use it as the #11, sustain it over the chord, and include it in motions such as 3–#4–5, 5–#4–3, 2–3–#4, and 6–5–#4.

Degree #4 lies a whole tone above the major 3rd, so it avoids the sharp minor-2nd clash produced by a natural 4 over an ordinary dominant seventh chord. It still forms a tritone with the root and retains clearly audible tension.

Degree 2 functions as a natural 9, while 6 functions as a natural 13. Over 13#11, both may be treated as stable extensions. Lines can be organized around the arpeggio 1–3–5–b7, with 9, #11, and 13 inserted between the chord tones.

Over a tritone substitute, follow the voice leading into the next chord rather than thinking only in terms of the scale. Over Db7#11–Cmaj7, for example, the notes of Db7 can move to the nearest notes of Cmaj7: Db falls to C, the major 3rd F may fall to E, and the minor 7th Cb remains as the common pitch B after enharmonic reinterpretation.

Do not mechanically run the parent Melodic Minor scale from its tonic. The root of the current dominant seventh chord must remain the center, so place 1, 3, 5, and b7 on structural beats and use #4 as the defining extension. When the harmony requires a natural 4, b9, #9, or b13, choose a scale that contains those notes.

Lydian Dominant is the fourth mode of Melodic Minor and a dominant scale with the formula 1 2 3 #4 5 6 b7. The major 3rd and minor 7th establish the I7 foundation, while the raised 4th adds the defining #11. Its natural 9 and 13 make it suitable for 9#11 and 13#11 chords. Its principal applications are dominant seventh chords with a #11, non-resolving dominant harmonies, and tritone substitutions.