The minor7b5 chord is found diatonically across major and minor scales but is often misunderstood, or worse, poorly applied.
This article will focus on the basics of this chord and it’s applications in three primary scales: Major, Harmonic Minor, and Melodic Minor. Essentially, this chord presents a darker, brooding character, and composers and arrangers who understand it’s application can often times create dynamic tensions and resolutions in their harmonies.
CONTEXT
We must first start with the spelling of the chord and it’s central role in major and minor scales. Let’s start with the C Major scale and review the diatonic scale line of seventh chords:
C Major Diatonic 7th Chords:
I = C Maj7
II = D min7
III = E min7
IV = F Maj7
V = G7
VI = A min7
VII = B min7b5
I = C Maj7
The minor seventh flat 5 (-7b5) chord is located at the seventh position, and is often referred to as “half diminished” or “minor seventh flat five”. In major, it can take the parent major scale, and harmonically can be used in a sequence of 5th related chords:
C Maj9 | F Maj7 | B min7b5 | E min7 | A min9 | D min7 | G7 | C Maj7
In addition, the min7b5 chord may be viewed as an extension of a dominant chord (G9) because it’s root (B) is the 3rd of G7, the fifth degree of the major scale. This rule holds true for all major keys, that is, the root of the half diminished will always lie a major 3rd below the root of the parent (C major) dominant 7th chord (G7). Further, the min7b5 chord possesses a Tritone between its root (B) and its flatted 5th (F). In major, the half diminished chord influences the preparation of a chord progression to a relative V7 chord and to a substitute V7 chord, most common the bII7.
In addition, the half-diminished chord is also related to it’s brother, the diminshed seventh chord primarily because of it’s role as a passing tone. The term “half diminshed” is used because the 7th degree of the chord is flat, not double flatted as in the diminished 7th chord. Example, B min7b5 (B, D, F, A) and B dim7 (B, D, F, Ab).
Let’s now examine the min7b5 chord in Minor.
HARMONIC MINOR
In the harmonic and natural minor scales, the minor7b5 chord is found at the second position and is most successfully used there.
Harmonic Minor scale in 7th chords:
i = C min(maj7)
ii = D min7b5
III = E maj+5
iv = F min7
V = G7(b9)
VI = Ab Maj7
vii = B dim7
The minor seventh flat five chord is found in the second position and functions well in the minor i, ii, V, i progression. Because the parent minor scale is diatonic to all chords in the minor ii, V, i sequence, the improviser can use the harmonic minor scale when playing through this progression. When you add the b9 and b13 tensions to the V chord, you produce a melodic sequence of minor tonalities and color resolving to the tonic minor. It works well because of the common tone, Ab, in both the ii-7b5 and V7b9 chords. The flat 13th in G7 (b9b13) lends nicely to the minor 3rd of the tonic, in this case, Eb for C Harmonic Minor. For example, here is the i, ii min7b5, V7(b9), i progression in C Harmonic Minor:
C minor(Maj7) | D min7b5 | G 7(b9, b13) | C min(Maj7).
When playing through these changes, the soloist is encouraged to identify the common tones existing throughout the chords. Namely, we can easily spot the following common tones among D min7b5 and G7b9b13: D, F, Ab. In terms of leading tones, one can now see how the 7th in D min7b5 (C) resolves a half step downward to B, the 3rd of the G7 chord. From G7b9, we see how the b9 (Ab) resolves downward a half step to G (5th of C min) and the 5th of G7b9 (D) resolves up a half step to the 3rd of the tonic C min chord, which is Eb. Also, as described above, adding the b13th to the G7 chord produces a common tone with the tonic minor (Eb).
MELODIC MINOR
When we examine the Melodic Minor scale, we see the half diminished chord is located in the sixth degree of the scale:
i min(maj7
ii min7
III+maj7
IV7 (#11)
V7 (b13)
vi min7b5
vii dim7 (altered dominant).
Unlike the major scale, the melodic minor scale produces two tritones: the first occurs between the third and sixth degrees, and the other tritone occurs between the fourth and seventh. In melodic minor, the minor7b5 chord usually functions best as a tonic minor sound. When played and arranged as the sixth degree, the min7b5 chord is most often used as part of a deceptive cadence.
The Locrian (with natural 2nd) mode can be applied to the min7b5 chord. Given the complex tonality of the Locrian mode, the 9th degree is often used to provide more stability. For example, in C Melodic Minor, the sixth degree would be Amin7b5, and by adding the 9th (B), you produce a common tone with the natural seventh of the tonic minor, C min(maj7).
While additional uses of the min7b5 chord can be explored, especially as part of a deceptive cadence, the purpose of this introductory article is to ground the player to the harmonic structure and function of the chord in Major, Harmonic Minor, and Melodic Minor scales. The possibilities for application now rest with you, the composer and soloist. Taking some time to understand the role of the min7b5 chord can open doors to your arrangements and your playing.
