Is there a musical term for two different chords that contain the same notes?
E.g., Bdim7 is B D F A♭ and Ddim7 is D F A♭ B. They both have the same notes but their names are different.
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1For what it's worth, I personally find the adjective "enharmonically equivalent" much more common than any noun that relates these chords.– RichardAug 17, 2018 at 15:05
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2 Answers
Typically, they are just considered named inversions.
Fully diminished chords and augmented triads like in your example have a very specific concepts tied to the symmetric nature that makes multiple names possible. These chords are known as symmetric chords because they are built using just one kind of interval. If you build a chord by going up in minor 3rds you get a fully diminished 7th and if you build a chord by going up in Major 3rds you get an Augmented triad.
These chords have been informally called enharmonic chords on the site, but that's not a formal term.
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That's one type of pitch set with multiple names. We also need to consider Am7/C6, Bm7b5/Dm6...– LaurenceAug 17, 2018 at 0:32
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@LaurencePayne That's why the first sentence makes the distinction on the broader category and the last sentence gives them an informal name.– Dom ♦Aug 17, 2018 at 1:07
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Not sure I would see C6 as an inversion of Am7. Yes, they contain the same notes/pitches, but they would be named as each, depending on their function, surely?– TimAug 17, 2018 at 6:43
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Actually, I thought "enharmonic chords" was the correct term when the spelling of the chords is different, but I don't have a reference to back that up. It's a logical extension of enharmonic notes, of course.– user19146Aug 17, 2018 at 6:53
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1I would see C6 and Am7 as two different names for the same chord, not "two different chords". The only reason for the two names is the theory of harmony that we currently use. Back in the baroque era, when chords were named from the intervals they contained not from some assumption about their "roots", C6 and Am7 had the same name using figured bass notation , and neither composers nor performers had any problems with that! The first book that introduced the ideas of chord inversions etc was published in 1744, and at the time was widely considered "avant garde theory" not "mainstream".– user19146Aug 17, 2018 at 6:56
There are only three fully diminished chords in regards to actual pitch. They can be spelled different ways according to the key. Your example for Ddim7 is actually spelled incorrectly. It should be D F Ab Cb. The Cb is what shows the quality of the dim7, not a B. That would just be a M6 above D.
Schoenberg called these chords vagrant chords as "such a chord belongs to no key exclusively; rather, it can belong to many, to practically all keys without changing its shape (not even inversion is necessary; it is just to assume relation to a root.) p.195 of his Theory of Harmony.
answered Aug 17, 2018 at 2:44
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1Vagrant chords -- I haven't heard that before, but that is a nice term.– user39614Aug 17, 2018 at 3:19
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@heather-s Actually, there are only 3 fully diminished chords. Also, I don't think I'll ever get used to things like Cb or Abb. Yucko!– S. ImpAug 17, 2018 at 17:37
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1@S.Imp, yes, you are right about the three. I had gotten myself mixed up. I will edit my answer. Aug 17, 2018 at 18:17