Diminished (fully and half) vs. ii-7b5

Differentiation Between Diminished, half-diminished, and minor 7thb5 chords and scales. Understanding the diminished resources include half/whole and whole/half scales and that chords are fully or half-diminished, but then the minor 7thb5 is diminished (d minor 7 b5 = )D- F,-Ab, C), but the scale source can be derived from the 6th mode F melodic minor. I would like to better understand the ‘real-world’ differences and applications in actual songs.

Hi @landermaestro :wave: great question here.

Firstly to clear up some terminology, the term “half diminished” and “minor 7thb5” both refer to the same chord type.

I personally prefer to use “minor 7th flat 5” but you will hear jazz musicians use both terms.

Understand that “C half diminished” and “C-7b5” both refer to a chord built from the chord tones C-Eb-Gb-Bb.

The main ‘real-world’ difference between -7b5 chords and diminished chords is their function and application in harmony.

  • The -7b5 chord functions as the ii chord in a minor 251 progression, and it can also be substituted for the ii-7 chord in a major 251. In this sense I like to look at the -7b5 as a specific ‘flavour’ of minor chord that is diatonic in minor keys, and can be used as a substitute in major keys.

  • The diminished chord has more varied applications. The most common application I see in jazz standards is when diminished chords are used in place of a V7 chord in a 251. Each diminished chord functions as 4 different rootless dom7b9 chords. Using diminished chords in this way creates different colours and textures in a V-I cadence.

  • Diminished chords are often used passing chords outside of 251 progressions. Bar 3 of “Pure Imagination” is a nice example and I cover the same movement in this lesson of my cocktail improv course.

  • Diminished chords can also be used to ‘soften the landing’ into the 1 chord in a 251 progression.

  • Diminished chords are also used in block chords and the 4-way close voicings.

  • Another application of diminished harmony would be Barry Harris Voicings. Forum thread with exercises here, and regular video lessons part 1 here and part 2 here.

  • That’s the main applications I can think of, and as you can see Diminished Chords have much more varied applications than -7b5 chords aka. half diminished chords.

  • Diminished chords often function as ‘dominant chords in disguise’. This helped me a lot of with my initial understanding of them when analysing how they appear in jazz standards.

From a scale perspective, we have the diminished scale which can be played over both diminished chords and the related altered dominant chords (due to the rootless dom7b9 relationship I highlighted above).

For half diminished chords, ie. minor 7th b5 chords, common scales to derive melodies over this chord type are the Locrian Mode (7th mode of the major scale) and the Locrian Natural 2 which as you correctly point out is the 6th mode of the melodic minor scale.

To learn about the improvisation possibilities for the ii-7b5 chord, check out @Tuomo’s 2 Minor Harmony Workshops that will take place this month:

The dates of the workshops are Friday 18th and Monday 28th November.

Any follow up questions with this please post them here and I’m happy to help out further.