• Week 10: Half-Diminished Seventh Chord + Cheat Sheet

    in Chords & Progressions,Piano

    half-diminished seventh

    In today’s post, we’ll be exploring the half-diminished seventh chord.

    The half-diminished seventh chord is not as common as the major, minor, and dominant seventh chords, but, nonetheless, very important in harmony.

    The half-diminished seventh chord is formed from the seventh degree of the major scale and is rarely used.

    In this post, we’ll be covering the ins and outs of the half-diminished seventh chord; starting from its basic definition, then delving into its intervallic breakdown where you will understand the intervals that make up this week’s chord.

    I’m also going to show you alternative approaches to its chord formation – the scale approach, the interval approach, and the chord approach.

    I am glad to welcome you to week 10 of our FREE 16-week chord revival program. Let’s go!

    The Half-Diminished Seventh Chord – Defined

    The half-diminished seventh chord is a chord formed off the seventh degree of the major scale. To help you understand more about this chord, I’ll make a reference using the C major scale.

    In the C major scale, B:

    …is the seventh tone. The half-diminished chord is simply the chord formed off this seventh tone (B, in this case). Using my pick-skip technique, all you just need to do is start on B:

    …skip C and pick D:

    …skip E and pick F:

    …skip G and pick A:

    If we put all the notes we’ve picked together, we’ll have B, D, F, and A:

    …and that’s the half-diminished seventh chord. Here’s what it looks like if transposed a half step up to C:

    In the ensuing chapters, we’ll break down this chord into its intervallic components so that you’ll understand why this chord is called the half-diminished seventh chord.

    A Breakdown Of The Half-Diminished Seventh Chord

    The goal of this segment is to breakdown this chord into its intervallic components.  This is a fancy way to say the intervals that make up the chord.

    Every chord, no matter how small or large, no matter how complex or simple, can be broken down into smaller harmonic fragments known as intervals. An interval is basically the relationship between two notes as it relates to distance.

    So using the C half-dim 7th chord as a reference, we have…

    C and Eb:

    …which is a minor third.

    C and Gb:

    …which is a diminished fifth.

    C and Bb:

    …which is a minor seventh.

    “Why are we covering the intervallic components of the half-diminished chord?”

    The intervallic components of a chord help you understand these two things:

    • Its quality
    • Its stability

    Check out what each of these intervals represent…

    The minor third

    The interval formed between the root and third of a chord determines its quality – whether it is major or minor. The half-diminished seventh chord is a minor chord quality because the interval between its root and third is a minor third.

    The diminished fifth

    The diminished fifth is an unstable interval.

    It was called the devil in music several centuries ago and popularly known today as the tritone. The diminished fifth interval is unstable as opposed to the perfect fifth interval. Every chord that has a diminished fifth interval is unstable and the half-diminished seventh chord is no exception.

    The minor seventh interval

    The minor seventh interval is a dissonant interval.

    However, this interval contributes to the quality of the half-diminished seventh chord. The interval between the third and seventh chord tones of the half-diminished seventh chord is a perfect fifth.

    Using C half-dim 7 seventh chord as a reference:

    …the interval between Eb and Bb:

    …which are the third and seventh tones of the half-diminished seventh chord are a perfect fifth apart. For all intents and purposes, the perfect fifth interval is considered to be universally consonant.

    Therefore, the half-diminished chord is a combination of stability and instability. Stability between its third and the seventh chord tones (Eb and Bb):

    …and instability between its root and fifth (C and Gb):

    …as opposed to the diminished seventh chord, which has absolutely no degree of stability.

    Now that you’re familiar with the intervallic components of the half-diminished seventh chord, let’s go ahead and explore its formation.

    Approaches To The Chord Formation Of The Half-Diminished Seventh Chord

    In this segment, we will be talking about chord formation approaches and like I promised in the beginning, we’ll be covering three approaches to the chord formation of the half-diminished seventh chord.

    Scale Approach To The Chord Formation Of The Half-Diminished Seventh Chord

    The very first approach to the formation of the half-diminished seventh chord will feature the use of scales. This is called the scale approach because we are going to be using a known scale to form the half-diminished seventh chord.

    The scale we are using in this chord formation method is an old scale system known as the locrian mode. The locrian mode is the seventh mode and it is naturally formed on the keyboard from B to B:

    …all white notes.

    Earlier in the beginning, I defined the half-diminished seventh chord as a chord of the seventh degree of the major scale.

    At this point, you should be seeing how synonymous the half-diminished seventh chord is with the number seven.

    It is the chord of the seventh degree and it’s also formed from the seventh mode [the locrian mode.]

    “How do I form the locrian scale in all the keys?”

    The formation of the locrian scale is pretty simple!

    To form the locrian scale in all the keys, all you need to do is to think in terms of the major scale of the key a half step above the note of the locrian mode you want to form.

    If I want to form the C locrian scale, all I need to do is to think in terms of Db. The Db major scale can help you derive the C locrian scale and this is because the C locrian scale is simply the rearrangement of the notes of the Db major scale:

    …from C to C:

    Starting from C:

    …If I continue to add other tones of the Db major scale to it…

    I’ll add Db:

    …add Eb:

    …add F:

    …etc. until I get to C again:

    This works because C is really the 7th tone of the Db major scale. Playing the Db major scale from the 7th degree to the higher 7th degree produces the locrian mode.

    Here’s one more example…

    If I want to create the F locrian scale, all I need to do is to think in terms of the major scale whose root is a half step up from F and that’s the Gb major scale:

    Starting from F:

    …I will continue to add other tones of the Gb major scale to it…

    I’ll add Gb:

    …add Ab:

    …add Bb:

    …add Cb:

    …etc. until I get back to F:

    What’s really happening is I’m playing the Gb major scale from the 7th degree (F) to the higher 7th degree (F).

    For reference purposes, here are the locrian scales in all twelve keys:

    C locrian scale:

    C# locrian scale:

    D locrian scale:

    D# locrian scale:

    E locrian scale:

    F locrian scale:

    F# locrian scale:

    G: locrian scale:

    G# locrian scale:

    A locrian scale:

    A# locrian scale:

    B locrian scale:

    The half-diminished seventh chord can be formed using the locrian scale if you are familiar with my pick-skip technique.

    All you need to do is pick a note and skip the next note until you get to the seventh tone of the locrian scale.

    Here’s the scale approach to the formation of the C half-diminished seventh chord using the C locrian mode:

    Starting from C:

    …skip Db and pick Eb:

    …skip F and pick Gb:

    …skip Ab and pick Bb:

    So put together, C, Eb, Gb, and Bb will produce the C half-diminished seventh chord:

    Following this procedure using any of the locrian scales we covered, you can form the half-diminished seventh chord in all the keys.

    Interval Approach To The Chord Formation Of The Half-Diminished Seventh Chord

    The next chord formation approach is the use of intervals.

    The intervallic breakdown of the half-diminished seventh chord showed us three intervals that it consists of – the minor third, the diminished fifth, and the minor seventh intervals.

    Stacking these intervals in one octave will produce the half-diminished seventh chord.

    The minor third interval can be formed in any key from the relationship between the first and third tones of the locrian scale in that key. The diminished fifth is formed from the relationship between the first and fifth tones of the locrian scale while the minor seventh is formed from the relationship between the first and seventh tones of the locrian scale.

    Stacking the minor third, the diminished fifth, and the minor seventh intervals together in one octave will produce the half-diminished seventh chord.

    In the key of C, the half-diminished seventh chord consists of…

    C and Eb:

    …a minor third.

    C and Gb:

    …a diminished fifth.

    C and Bb:

    …a minor seventh.

    Stacking all these intervals in one octave would produce the C half-diminished seventh chord:

    Now, let me show you in a couple more keys…

    Example #1 – F half-dim 7

    The F half-diminished seventh chord can be formed by stacking the three intervallic components in the key of F…

    F and Ab:

    …a minor third

    F and Cb:

    …a diminished fifth.

    F and Eb:

    …a minor seventh.

    Stacking these together in one octave will form the F half-diminished chord:

    …which consists of F, Ab, Cb, and Eb.

    Example #2 – A half-dim 7

    The A half-diminished seventh chord can be formed by stacking the three intervallic components in the key of A…

    A and C:

    …a minor third

    A and Eb:

    …a diminished fifth.

    A and G:

    …a minor seventh.

    Fitting this together in one octave would produce the A half-diminished seventh chord.

    Chord Approach To The Chord Formation Of The Half-Diminished Seventh Chord

    Our last chord formation technique for today favors the use of a known chord. In a previous post, we covered the minor seventh chord and I trust that you are familiar with it.

    You can lower the fifth tone of any known minor seventh chord by a half step to produce the half-diminished chord. Using the C minor seventh chord as an example:

    If the fifth tone (G):

    …is lowered by a half step (to Gb):

    …we’ll have the half-diminished seventh chord:

    Here’s, side-by-side, the minor seventh chord and the half-diminished seventh chord in all 12 keys:

    C minor seventh chord vs C half-dim 7 chord:

    C# minor seventh chord vs C# half-dim 7 chord:

    D minor seventh chord vs D half-dim 7 chord:

    D# minor seventh chord vs D# half-dim 7 chord:

    E minor seventh chord vs E half-dim 7 chord:

    F minor seventh chord vs F half-dim 7 chord:

    F# minor seventh chord vs F# half-dim 7 chord:

    G minor seventh chord vs G half-dim 7 chord:

    G# minor seventh chord vs G# half-dim 7 chord:

    A minor seventh chord vs A half-dim 7 chord:

    Bb minor seventh chord vs Bb half-dim 7 chord:

    B minor seventh chord vs B half-dim 7 chord:

    Attention: The half-diminished seventh chord is also known as the minor seventh flat five because it can be literally formed from a minor seventh chord whose fifth tone is lowered by a half step.

    Final Words

    I am thrilled you’ve made it to the end of this lesson and I am confident that you have everything you need to form half-diminished seventh chords in any key using a variety of chord formation approaches.

    The half-diminished seventh chord is one of the essential chords in playing the minor 2-5-1 progression.

    Therefore, the half-diminished seventh chord is one of the essential seventh chords that should be in the chordal vocabulary of every serious pianist or musician.

    That will be all for today.

    Ciao!

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    Hello, I'm Chuku Onyemachi (aka - "Dr. Pokey") - a musicologist, pianist, author, clinician and Nigerian. Inspired by my role model Jermaine Griggs, I started teaching musicians in my neighborhood in April 2005. Today, I'm privileged to work as a music consultant and content creator with HearandPlay Music Group sharing my wealth of knowledge with thousands of musicians across the world.

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    { 2 comments… read them below or add one }

    1 Peter LaFosse

    Another great blog, I understand it a lot better now, thank you .

    Reply

    2 John Tuohy

    Very interesting and well explained,I think I’ve grasped it.Thank you.

    Reply

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