In my experience and training, I'm under the impression that a diminished triad isn't listed in a chord chart unless it is considered the Diminished 7th chord function. While there may be different functions for diminished chords, in my experience, the Locrian mode is used for the m7(b5) chord, not the diminished chord.

I say that the min7(b5) chord isn't to be hidden behind the "Diminished Triad" label. The diminished chord has a bb7, and the min7(b5) doesn't include that. If you're using Locrian over the diminished triad, it's a mislabeled min7(b5) chord, no?

4 Answers 4


When using the entire seven notes of Locrian, then yes, the half-diminished seventh chord is implicitly involved. However, it's perfectly plausible to use Locrian with a diminished triad without implying a half-diminished seventh chord -- just avoid playing the seventh. The first five notes encompass a diminished triad, so will work fine over that chord. The only issue would be whether the second scale degree fits the larger musical context.


It's pretty straightforward that m7♭5 and a diminished triad aren't the same. Take Co - the triad - C E♭ G♭. Add the diminished 7, B♭♭ (enharmonic with A). Not the same notes as Cm7♭5 - C E♭ G♭ B♭. Although the basic triad is the same, the extensions are different.

C Locrian contains the notes C, D♭ E♭ F, G♭, A♭ B♭. Thus, the better match from the two above chords will inevitably be Cm7♭5, as the B♭♭ note will certainly clash from the C fully diminished 7th.

However - it would really depend where certain notes were played and there's not a lot wrong with passing notes, on non-stressed parts of bars. Or even notes which seemingly, technically don't/won't fit, but when played, add some tension to that part of the piece.

  • "m7♭5 and a diminished triad aren't the same."... do you mean a dimished tetrad? The first 3 notes (triad) are the same, aren't they?
    – mkorman
    Commented Mar 15, 2021 at 9:59
  • @mkorman - no, that's what I meant - they can't be the same, one has 3 notes, one has 4. Read on...
    – Tim
    Commented Mar 15, 2021 at 10:02

A dimished chord (with the ♭♭7) is not part of any diatonic scale. Thus, no diatonic mode will really fit it 100%. When playing over a dimished chord you need to think outside the modes and use an altered scale.

As mentioned above, the issue is the ♭♭7 vs. the ♭7 of a diatonic semi-diminished chord. You could start with the Locrian mode and add a ♭♭ alteration to the 7th.


"If you're using Locrian over the diminished triad, it's a mislabeled min7(b5) chord, no?"

No, because one is a triad. That would be like saying that a major tried is a mislabeled dominant 7th chord, or a mislabeled major 7th chord.

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