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If I am in D minor and want to write a Bbm chromatic mediant chord, will I have to write the Db, even though in surrounding bars I have the usual C# for the raised LT?

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    NB: This is the Darth Vader chord progression.
    – Richard
    Feb 9, 2023 at 1:39
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    It would be better if we could see those 'surrounding bars', to get some idea of the actual prevalent harmonies, and their make-up. We only have your word that it's the chord you say (see answers).
    – Tim
    Feb 9, 2023 at 8:56

5 Answers 5

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You cannot write C♯, as the chord itself would not have a C♯ in it. It would of course have D♭ in its normal spelling, so that's what to use.

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    precisely. And, to OP, you can think of it a bit like a "homophone". The fact that C# (the raised 7th of D minor) and Ab (the minor third of an F minor chord) sound at the same pitch (in standard 12 tone equal temperament), is kind of like a musical "homophone"; like the words "sell" and "cell", here the Ab and the G# mean different things, but sound the same on their own.
    – Some_Guy
    Feb 8, 2023 at 22:47
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    @Some_Guy don’t you mean: “Db (the minor third of a Bb minor chord)” ? Feb 8, 2023 at 23:37
  • yes I do. Apparently I switched key to A minor halfway through my comment, sorry for the confusion! 🤦‍♂️
    – Some_Guy
    Feb 9, 2023 at 0:04
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It's actually a good question. Normally, C♯ is far more plausible in the key of D minor than D♭ is. Yet, as the other answers are saying, the B♭m chord contains D♭, not C♯, no way around that.

However, if surrounding bars contain a clear C♯, then I would put some doubt whether that chord really acts as the chromatic mediant B♭m. What seems more likely to me is that you're essentially dealing with a diminished seventh chord C♯°⁷, which does contain the notes B♭ and C♯. Granted, it also contains E and G instead of the F of the B♭m chord, but double check on that note – does it feel like a suspension?
If yes, then this isn't a B♭m chord and the note should indeed be labelled C♯. Like in this sketch:

X:1
L:1/8
M:C
K:Dm
%%score T1 T2 A B
V:T1           clef=treble
V:T2           clef=treble
V:A            clef=alto
V:B            clef=bass
% 1
[V:T1]  fe  g(g      g3/2)d/2 ^c3/2d/2   | d4
[V:T2]  A(G G)D/2E/2 F(E       E)G       | F4                
[V:A]   D2  C2       B,2       G,A,/2B,/2| A,4
[V:B]   D,2 E,D,     ^C,2      A,,^C,    | D,4

Here, looking at beat 3 in isolation would suggest a B♭m in first inversion, but the context makes it clear it's actually a C♯°⁷ with the E suspended(?) to F.

(Not sure this would be called a suspension.)

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  • I'd say the F is just an accented upper neighbor.
    – Richard
    Feb 9, 2023 at 1:39
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By rules of enharmonicity both variants are principally okay, and there are reasons for the use of both cases. Spelling the note as Db does have the quite obvious advantage that it make comprehension of harmony much easier. But this is not the only thing you want to consider when writing scores. Especially when you are scoring for multiple voices this might lead to weight lines, such as if an instrument before had a C# and then the Db, or even if the line were to descend E-D-?.

E.g. in Berlioz’ Requiem he has this passage:

enter image description here

Here the Bb minor is spelled as F with augmented 3,5, which absolutely does not make sense harmonically. But due to the progression F#7 - Bbm this notation is easier to read for the middle voices (this is one heck of a progression by the way, based on a chromatically descending bass: G - F# F#7 - Bbm/F - F - Gb Ebm - Bbm).

Also I remember a piano piece featuring the spelling G-A#-D (I just do not remember what it was though ...).

Point is: It is your responsibility as composer, arranger or editor to decide whether this should be spelled such or such. And there will not be a fixed rule for when to do what, as this will depend on the music around the note in question. Try out both variants and try to estimate which would be more clear and which would be more confusing to play. The art is of course to always select the one that is more confusing :).

But when in doubt you should probably tend towards the harmonically correct spelling and go for Db.

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  • Not exactly the same progression as the OP, but I think the does illustrate the linear issues well. Feb 9, 2023 at 15:06
  • Nice find. However, I would argue that Berlioz has made a dubious decision already earlier: writing it as F♯7. To me, this is a G♭ augmented sixth chord, which would resolve to B♭m without the awkward enharmonic discrepancy. Feb 9, 2023 at 15:23
  • @MichaelCurtis Not exactly the same progression, yes, but in fact not too different, considering Berlioz goes from G major to Bb minor. Anyway, it was not really about this exact progression, but about giving an example of why it could make sense to spell notes in the harmonically wrong way.
    – Lazy
    Feb 9, 2023 at 18:46
  • @leftaroundabout But it clearly is a F#7. Berlioz starts G major and uses a 5-6 leading to F# major. In this context G major takes the function of a VI in B minor, leading to a dominant, which is not an uncommon progression. On the other hand the resolution F#7 to Bbm is not exactly common. You’d need to argue that actually Berlioz should have written the start as Abb major, but even then reading F#7 as Gb augmented 6 seems a little bit deliberate to me. But then, the whole thing does of course strongly build on avoiding clear cadences and keeping tonality vague.
    – Lazy
    Feb 9, 2023 at 20:38
  • @Lazy, don't misunderstand me, I think this is a great example for comparison and a great answer. Feb 9, 2023 at 23:11
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You use Db. Since it's a chromatic chord, you are leaving the primary key signature, even if only for that one moment. Thus, the chord is spelled according to its root.

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    A chromatic chord doesn't mean you're 'leaving the primary key'. It's a chromatic chord IN the primary key, not a diatonic one in some other key. This feeds the common misapprehension that only diatonic notes/chords are 'allowed'.
    – Laurence
    Feb 9, 2023 at 12:49
  • @Laurence Thanks. I see now why my post was misunderstood. I think I've cleared it up.
    – Aaron
    Feb 9, 2023 at 15:42
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If I am in dminor and want to write a Bbm chromatic mediant chord

You've answered your own question. If you want to write a B♭m chord, spell it like a B♭m chord.

If, as has been suggested, we're talking about 'Imperial March', it clearly IS a B♭m chord. If, as has also been suggested, it can be more usefully analysed as C♯°⁷, spell it that way.

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