Here's a time-waster of a question, because it doesn't REALLY matter...I'm just curious.
When writing out chords for a song, how does one determine the "correct" name for the diminished (or dim7)?
There are only three diminished chords really, so they have duplicate names.
Example:
Writing out chords for a song in C major...if I need to use a Bdim, I would call it a Bdim rather than an Fdim or Ddim, mainly because Bdim is a triad naturally occurring in a C major chord scale (it is the 7th)...is this correct ?
HOWEVER, if in that C major song, I need to use an Edim7, why should I call it that, instead of a C#dim7, or a Gdim7, or a Bbdim7 ?...and if so, why ?
Same thing applies to augmented chords.....picking the "right" name has to be a theory-based rule...doesn't it ?
thanks.
"A child of five could understand this...send someone to fetch a child of five !"--Groucho Marx
Hi,
As you say, it's a quirky bit of theory, but here goes.
If you're using the notes B, D and F in the key of C it can "only" be a Bdim chord because the "F-chord" in the key of C is F Major, and the chord built on D in the key of C is Dm. Likewise, you couldn't really call an Edim7 in the key of C a C#dim7 because C# doesn't exist in the key of C. Nor does Bb. My logic falls over with the Gdim7 version. Tom can no doubt explain it all a lot better
Hope this helps.
A :-)
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Yep, there's a rule based on roots. You want the name to make sense in the context.
Let's say you're playing a Cº7, C-Eb-Gb-Bbb(A). All four can be valid names for the chord in isolation.
So you look at where the chord is placed in the progression. Let's say you're in the key of C - you probably won't give it an out-of-key name (Eb or Gb).
Next you look at the root motion - the chords immediately before and after it. The most common root motion is by fifths or fourths; if the chords on either side are F/G roots, it's probably a Cº7; if they're D/E roots, it's probably Aº7.
One big exception to that - I'm assuming that the º7 chord has a big role - that it's held for several beats or otherwise emphasized. If it's just a quick passing thing, preference would be given to a chromatic motion - G-Gbº7-F makes more sense squeezed into one measure; G-Cº7-F makes more sense if it's a whole phrase. (Edit for clarity: I don't necessarily mean G and F major chords - they can be any chord type, since it's just the root motion that matters)
Now if that didn't give you a clear name, there are only two more motions available - seconds/sevenths and thids/sixths. Chords tend to move in step a lot more often than they move in thirds - since chords are built on thirds, this motion leads to very bland music - you'll have two voices overlapping in just about every change (that's why the transition to a relative minor sounds so smooth - Am and C share two notes... but you wouldn't go Dm-F-Am-C-Em-G, or have any other long string of chords by thirds, or you'll put the audience to sleep!)
So if the chords on either side have roots B/D, it's probably Cº7, and if they're G/B, it's probably Aº7. Notice you need the chords on both sides to figure it out - moving in from a B root could lead to either name; it's by knowing the whole set of motions that you properly name chords.
The same thing is true of augmented chords - and other chords too. C6 and Am7 have the same notes; you need to figure out how the roots are working to decide on the right name.
Guitar teacher offering lessons in Plainfield IL
Thanks for the responses.
My progression is from a 1928 oldie named "Makin' Whoopie", end of verse, to start of Bridge:
end of verse:
G7 C C/B
Bridge:
Edim7 Dm Fm6 C C/B
Edim7 Dm Fm6 C G7......to verse
regards
"A child of five could understand this...send someone to fetch a child of five !"--Groucho Marx
