The Better Half: Navigating the m7b5 Chord -

The Better Half: Navigating the m7b5 Chord

“Night And Day.” Your singer has his mojo on—bow tie flapping in the wind machine—wedding party in the palm of his hand.
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“Night And Day.” Your singer has his mojo on—bow tie flapping in the wind machine—wedding party in the palm of his hand. Then you hear that sound again. The word “near” lands squarely on an F#m7b5 chord. The sound of the half-diminished chord underlines the urbane Cole Porter lyric. What does a bassist need to know about half-diminished chords? Let’s explore three ways that these not-quite-minor, not-quite-diminished chords are used, and how to navigate the sound on the bass.

The half-diminished chord is also called minor 7 flat 5. You should know both terms. Several chord symbols describe the sound: Cm7b5, Cm7(b5), C–7b5, and Cø7.

Last month, we looked at other basic chord types: maj7, m7, 7, and dim7. This Woodshed focuses on the unique sound and function of the half-diminished (m7b5) chord. The flatted 5th defines the sound of the half-diminished in a bass line or solo. Listen to songs like “Softly As in a Morning Sunrise,” “Woody n’ You,” “How Deep Is the Ocean,” and “What Is This Thing Called Love?” and you’ll hear lots of half-diminished chords.

The difference between a minor 7 chord and a minor 7 flat 5 is easy to find—the name gives it away. Example 1 shows a typical jazz solo lick on a II–V–I progression: Dm7, G7, Cmaj7. The line starts on the 5th of the Dm7 (the note A). In Ex. 2, the lick is exactly the same, except the first note is the flatted 5th of the Dm7b5 chord (the note Ab). Mind-blower #1: Any minor-7 pattern can be adjusted to fit the half-diminished sound just by lowering the 5th of the chord by one half-step. Mind blower #2: Internet talking heads have recently parsed the mechanics of modal interchange, which is the practice of borrowing chords from parallel keys to create more colorful harmonies. A great example of modal interchange is heard at the end of each A section of “What’s New,” a jazz standard by swing bass legend Bob Haggart. Example 2 uses the chords from bars 6–7 of the A section of “What’s New.” The Dm7b5 is borrowed from the parallel harmonic minor (C minor), yet it resolves to C major.

When I audition bass players at jazz workshops or at the Maastricht Conservatory, I’ll first check their command of major 7, minor 7, and dominant 7 chords. Next, I test their ability to interpret half-diminished chords, for example by playing a bass line over the progression of “Blue Bossa” (Ex. 3). I want to hear a bassist playing lines using a flatted 5th on the half-diminished chord. If a bassist can successfully outline the half-diminished sound in a bass line, then I’ll listen to her solo lines and see if she also nails the flatted 5th when indicated.

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There are three common functions of half-diminished chords: (1) predominant, (2) dominant, and (3) diminished passing chord. In most cases, the half-diminished chord functions as a predominant chord, leading to the dominant chord in a minor key. The solo pattern in Ex. 4 shows a typical jazz line on a II–V–I progression in C minor. The Dm7b5 is the predominant chord to G7b9, which is the dominant chord resolving to Cm7 (the minor tonic chord). Check out the notes in Ex. 4, and notice they are all derived from the C harmonic minor scale.

Example 5 shows the C harmonic minor scale, with the notes of the Dm7b5 indicated. This is a common method to outline the sound of the minor II–V–I: Use the harmonic minor scale of the tonic minor, in this case C harmonic minor.

Example 6 travels further into the theory universe by using the F melodic minor scale to outline Dm9b5. The natural 9th (the note E) on the Dm9b5 creates a brighter, more stable sound than the b9 generated by the C harmonic minor scale. The note Eb on a Dm7b5 only sounds good as a passing note on a weak beat.

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The half-diminished chord can also function as a dominant chord. Example 7 presents the Bm7b5 chord and the B Locrian mode. The chord tones are indicated with whole-notes, and the other scale tones are written as stemless quarters. This is the 7th mode of the C major scale. The Bm7b5 chord in Ex. 8 could serve a dominant function, as a substitute for G7. Note the G9 chord, which contains the notes of Bm7b5.

Half-diminished chords also function as diminished passing chords, as previously mentioned in the Cole Porter song “Night and Day.” Example 9 shows the tonic (Cmaj6) of “Night and Day” moving into bar 9. The F#m7b5 is a passing chord leading into the long turnaround back to the tonic.

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The next time you’re playing a wedding gig, and you hear your singer wail the word “near” in the second eight bars of “Night and Day,” you’ll know that you’re playing a half-diminished passing chord. Then when he’s crooning “What’s New,” lean over to the keyboard player and whisper, “modal interchange … it’s so hip!”



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