I did a music exam today. one of the questions was build chord from the following shapes (with the root given on the staff):

  • mM2
  • AugM7
  • dimdim 6/5
  • Mm6

what is the algorithm behind this markings. I am especially perplexed form dimdim 6/5.

EDIT: I think I Added unnecessary confusion: by 6/5 i meant 6 over 5 (First inversion of seventh-chord). I just now realised the other meanings sorry for that:(

  • Given that such chord symbols are almost entirely the province of jazz lead sheets, it's surprising that they wouldn't have used commonly accepted chord notations for them. "dimdim 6/5" is just strange. May 1 '11 at 13:30
  • What is strange also here, is that AugM7 is directly a chord symbol but the 6 over 5 is a figured bass. @idober: how were the two dim placed relative of the 6 and 5 ? I will have to change my answer (again) :-)
    – ogerard
    May 1 '11 at 15:49
  • Given the inconsistencies ("mM" vs "Mm"), I suspect that these chord symbols and figured bass notations are haphazardly remembered from the originals. Can we get some clarification in the OP as to what exactly the notations were? Separate them using * (list items) perhaps. May 1 '11 at 15:55
  • @Rein Henrichs: the Mm and the mM is exactly what was written in the test (I actually scribbled those examples on my hand during the test)
    – iddober
    May 1 '11 at 20:09
  • Ah, so they are. Makes sense. May 1 '11 at 23:55

You can build algorithms to decipher these markings but they are a collection/juxtaposition of many different series of notations. You can describe the same chord in several manners and various level of abbreviations. So this algorithm would be a collection of branching cases. I think there are already online chord calculators.

The most perplexing one to you is quite a borderline case, and I am not 100% sure because it mixes notations from different traditions (figured bass and chord operators) in a way I have not seen before:

  • dimdim 6 over 5 Now that we know it was figured bass, let's start from the main symbol (6 over 5) which is the first inversion of a 7-th chord. With root C, we have C-E-G-B, inversed to E-G-B-c. If it is a diminished chord, it would give E♭-G♭-B-c. If the double dim is to mean that the 7th is diminished as well (not merely a minor 7th), it would mean E♭-G♭-B♭♭-c. In semitone count from the root it would give (3,6,9,12). You would write: fully diminished 7th chord first inversion or dim7/b3rd.

The second one is a classic:

  • AugM7 would be augmented major 7th. Start from the root, add a major third, an augmented fifth and a major 7th. Starting with C: C E G♯ B. You will find as notation among others +M7 or +Δ7
  • Exactly what I would've answered :) May 1 '11 at 13:19
  • It was quite laborious for me but it was fun immersing again in that notational chaos.
    – ogerard
    May 1 '11 at 20:45
  • 1
    @ogerard: I had never seen dimdim. I'd have written E♭-G♭-B♭♭-c as E♭°. All inversions of this chord are also dim chords in their first inversion, so why give 6 over 5 in that case? dimdim alone would give the exact same result...
    – Gauthier
    May 2 '11 at 6:43
  • @Gauthier: You are right, if you are free to choose the root E ♭ o is the simplest way for a keyboard since d ♭ ♭ is enharmonic of c. And as they were using figured bass, they should probably have used slashed 7 or little flats and slashes before the 6 over 5. @idober: When you see this kind of chords, it is very likely that there is a modulation going on.
    – ogerard
    May 2 '11 at 7:15
  • 1
    @ogerard about special chars in comments: low tech... copy and paste :)
    – Gauthier
    May 3 '11 at 8:47

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