I'm harmonising a tune I've written, in C major, and one chord which resolves to C major consists of B, Db(or C#), F and A. It seems to be a sort of tritone substitution, but I am struggling to come up with an appropriate name for it. There are several options, but their names all sound quite ugly. What would be the best name for the chord? What would be the reasoning behind your answer?
How embarrassing ! Don't know why A got morphed into another note. SORRY !!
It's not really in the key but you could call it a Db7#5 since the notes you have can be arranged as Db, F, A, and Cb. It is the simplest name and you could look at it as an altered chord borrowed from the Phrygian mode thus fitting in with resolving to C.
D♭7#5/B.
Commented
Jul 25, 2015 at 14:50
It is indeed a tritone sub of V. I hear it as a G9(b5) with the root (G) replaced by the b5 (Db). So as a chord with root Db it is a Db7/#5, as already pointed out in the other answers. Since it is a tritone sub I wouldn't look at it as "borrowed" from some other mode. Possible scales to play over it are the whole tone scale (of course the one including a G and a Db), and the Db altered scale. Note that the latter scale is (enharmonically) equivalent to a C major scale with the root shifted up by a half tone to Db.
This chord could be named Db7(5+)/B (Db7(5+) with B in the bass). It is a substitute dominant chord (a tritone away from G7, and sharing a tritone with G7 -- that is, F <-> B), altered in its fifth degree, and played in the third inversion (the 7th degree is used in the bass). Its best enharmonic spelling is B-Db-F-A, as Db and A are made to explicitly be a minor second and a major second away from C and G, respectively (C# would be an augmented unison away, which could be at least misleading).
As others have suggested, a tritone substitution is probably the best way to look at it. As an additional point of interest, it could also be seen as a form of Augmented Sixth chord on the b2 scale degree. The Db and B form the interval of an augmented sixth, and adding the F makes it an Italian augmented sixth. The French and German aug6th chords would include a G or an Ab respectively. AFAICT, there's no special name for your version of the aug6th chord (where an A is added).
It could be construed as Db7b13 (or C#7b13). The 5 is missing, but it often is in more complex chords, and would clash with the b13 if left in. That chord would be Db, F, (Ab), Cb, no 9th or 11th, but they don't HAVE to appear in 13 chords,and it's not strictly a 13 chord anyway - just a dom 7 with a b13; and Bbb.I'm going for Db rather than C# as the key is C.
The root of the chord, as given, is B -- thus, a vii chord -- because the resolution of the outer voices dominates the sound.
Db (i.e., bII) chord?In the canonical teaching of functional harmony, there are rules about how certain intervals are required to resolve. In particular:
Db7In the case of the OP chord, B-F, being a diminished fifth, resolves "inward" to C-E. F-B, as in a root position Db7 chord, resolves "outward" to E-C. (Note that this would also hold in a C minor context.)
X:1
M:C
K:none
L:1/2
"_d5"[Bf]"_M3"[ce] | "_A4"[FB]"_m6"[Ec] || [K:Cminor] "_d5"[=Bf]"_m3"[ce] | "_A4"[F=B]"_M6"[Ec] ||
Similarly, the B-Db, being a diminished third, resolves inward to C; Db-B would resolve outward to C. (Since the OP is in C major, the minor case is excluded.)
X:1
M:C
K:none
L:1/2
%%score (V1 V2)
V:V1 clef=treble stem=up
V:V2 clef=treble stem=down
[V:V1]_d c | B c ||
[V:V2]"_d3"B "_P1"c | "_A6"_D "_P8"C ||
Thus, so far, we have the following, given the OP voicing and the "rules".
X:1
M:C
K:none
L:1/2
%%score (V1 V2)
V:V1 stem=up
V:V2 stem=down
[V:V1] "as given"[_DF][CE] || "spaced out"[B,F_d][CEc] || "root position"[_DFB][CEc] ||
[V:V2] B,C ||
The A, being an inner voice, we can be a bit loose with and just let it resolve down to G. (We could also argue whether it's actually an A [#5, which should resolve upward] or a Bbb [b6/13, which should resolve downward], but let's not.)
X:1
M:C
K:none
L:1/2
%%score (V1 V2)
V:V1 stem=up
V:V2 stem=down
[V:V1] [_DFA][CEG] ||
[V:V2] B,C ||
The naming of this chord depends a great deal on its voicing. When voiced as a root position Db chord, the sound of the resolving Db, F, and B dominates -- particularly the outer voices.
X:1
T:Ⓐ sounds like Ⓑ
M:C
K:none
L:1/2
[V:V1] "Ⓐ"[_DFAB][CEGc] || "Ⓑ"[_DFB][CEc] ||
...it is exactly because the outer voices dominate that, as given, the B, F, and A resolution dominates.
X:1
T:Ⓒ sounds like Ⓓ
M:C
K:none
L:1/2
[V:V1] "Ⓒ"[B,_DFA][CEG] || "Ⓓ"[B,FA][CEG] ||
... the sound doesn't change much if you displace the Db by an octave.
X:1
T:Ⓒ2 also sounds like Ⓓ
M:C
K:none
L:1/2
[V:V1] "Ⓒ2"[B,FA_d][CEGc] || "Ⓓ"[B,FA][CEG] ||
... the given chord is either B7b5b9 or B∅7b9, which one being determined by the melody or other context -- or left ambiguous.
The given chord is a vii chord, rather than a bII chord.
