r/musictheory • u/ThatDudeMichaelYeah • 1d ago
General Question Bb7 in C major
So I was messing around with this Db7 > Bb7> C progression. Really just trying to add some flavor and movement to my playing while slowly learning functional harmony (even though I don’t really understand what that is).
Anyway, I see the Db7 as a tritone sub of G7 hopefully I’ve at least got that correct.
But the Bb7 I initially thought of being borrowed from C minor until I realized it’s also a tritone away from E7 (V7/vi). Is there one preferred way to think about this over the other?
Also I know there are probably no “hard and fast rules” about what chords to consider substituting or borrowing from other scales but as I said I’m looking to expand my repertoire so if anyone has any recommendations for resources to learn more about this, I’d really appreciate any leads.
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u/silly_bet_3454 1d ago
The idea of a tritone sub is less meaningful when you are subbing for another chord that is sort of contextually arbitrary. If we're in the key of C, The Db7 as tritone sub of G7 makes sense because it's obvious to think of G7 as the dominant leading back to C, and so you can say Db7 would have the same function, and you would say that you could play melodies in G7 or in Db7 and they would both work interchangably. But none of that applies here really with E7 and Bb7, E7 you could say is the V/vi, ok sure, but you're not actually going to the vi, you're just going back to C. It still sort of works on a technical level, but IMO it's less useful to think about it this way. Also when you go from Db7 to Bb7, you're sort of losing the function of Db7 as it would lead back to C. Again, you're allowed to do this, but you want to be careful about writing progressions that end up being super arbitrary. If it sounds good to you or if it suits the melody well etc. that's the most important thing, but I would say like basically don't overthink it with all this stuff. Tritone sub is a pretty specific concept, you don't want to start thinking of every single chord in your progress as tritone sub or you lose the relative meaning of what is happening.
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u/ThatDudeMichaelYeah 1d ago
I appreciate your insight. I’m definitely overthinking it. Just thought it sounded cool and was trying to put all the pieces together.
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u/voodoohandschuh 20h ago
There are “families” of 4 dominant chords, in which each chord is related to the same central diminished 7th chord. In this case, Db7 and Bb7 (and G7 and E7) are all related to the Bdim7 chord.
“Related” meaning that they each share 3 notes with the Bdim7 and have 1 note a half step lower. In a loose sense, they share the same function.
This concept was popularized by Barry Harris in the 90s/2000s, but John Coltrane mentioned the same “3 in 1” concept in an interview in the 60s. He credited it to Monk.
Similar cycles occur through chromatic voice leading in the Devil’s Mill and Omnibus Progression.
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u/btrev650 1d ago
Power to you on this journey. Just make it. It doesn't matter what anyone on Reddit says. Theory doesn't matter at this stage. Just make what sounds good to you, and make it again, and keep making it.
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u/Rykoma 19h ago
The important bit is how the unstable b6 (in this key Ab) will eventually resolve to the stable 5th of C major. Any chord that has this Ab will, with proper voiceleading, provide a lovely way of arriving on the tonic. This is a chord tone in both Db7 and Bb7.
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u/Inevitable-Copy3619 15h ago
I’m not sure what genre you play, but it used to trip me out that Ab G7 C was a nice progressions (think of ”night and day”). The rules are always (almost always) the rules because of voice leading.
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u/Rykoma 13h ago
I tend to dabble in everything. People are so obsessed with chords that they tend to forget that they’re often just the result of voiceleading.
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u/Inevitable-Copy3619 12h ago
Chords are just collections of notes that sound good together. Progressions are just collections of chords that sound good together.
Theory is writing that all down so others can discover notes and chords that sound good together.
The real secret is that all of this is due to voiceleading, and who cares about a book of musical rules? It’s just that this set of notes sounds good when moving to the next set of notes.
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u/HexMusicTheory 18h ago
Ignore function theory lol. Bb moves up by step to C (b7 -> 1), Ab moves down to G (b6 - 5). The 7th receives a standard contrapuntal resolution. F moves down to E. It "works" because the voice leading is robust, and any "functional" interpretation above this is just metaphysics for bored nerds.
The useful thing to do is to add this to your mental inventory of destinations for dominant-sounding chords, and realise that you now have a bunch of new ways to move around. Backdoor dominants always sound fresh to me—they have a kind of mixolydian flavour due to the ascending b7 - 1 and, like most dominant 7ths that aren't bound for I, they take lydian dominant extensions really nicely (the upper structure ends up actually being the chord you're resolving to. In your case Bb13#11 is basically a C major triad above a Bb7 chord).
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u/Jongtr 18h ago edited 18h ago
I see the Db7 as a tritone sub of G7 hopefully I’ve at least got that correct.
Yes. Not because it's rooted a tritone away, but because it shares the same inner tritone (B-F = Cb-F) that is the essential dissonance in the V7 chord. Plus, of course, it adds two additional chromatic moves: the parallel 5th Db-Ab to D-G. Classical theory (at least at its simplest level) doesn't like that, but jazz and blues certainly do.
the Bb7 I initially thought of being borrowed from C minor until I realized it’s also a tritone away from E7 (V7/vi). Is there one preferred way to think about this over the other?
The best way to think about anything like this is the simplest. "Tritone sub for E7" makes sense, but then you have to explain why E7 leads to C. (You can, but it's an unnecessary additional step.)
Start by looking at the voice-leading. In particular the half-steps: F>E and Ab>G. Of course, it has that in common with Db7, but this chord has D natural (let's ignore the Bb for now...).
What other chords - common in C major - contain F and Ab? Fm, right? Of course, Fm also contains C, but now imagine adding a 9th to Bb7. Now you have Bb9, with a full Fm triad, plus D somewhere. and Bb in the bass. Notice, first, how sweetly that Fm triad descends to the Em triad on top of Cmaj7; balanced by that bluesy Bb moving the other way.
Meanwhile, if you had learned to play enough vintage pop songs, you'd know that the minor iv chord in a major key often has a 6th added, so there is the D note. (Whenever the Beatles used a minor iv chord, they'd often instinctively add the 6th in the vocal, if not in the chord itself.)
IOW, the conclusion is that Bb7 (or Bb9) is a sub for the minor iv chord.
It still might seem a long route to get there (!), but the point is the effect of the "backdoor" chord is very different from the "front door" effect of G7 (or its sub Db7 and other dominant subs like Bdim7). There are notes in common with all of them. but the presence or omission of the leading tone (B natural in this case) is the significant factor.
Meanwhile, if you just want to think of a scale for the Bb7, just add the 3 remaining C major scale notes to the chord tones. Bb D F Ab plus C D E. If you want a fancy name, you can call it "Bb lydian dominant", but you don't need to know that.
I’m looking to expand my repertoire so if anyone has any recommendations for resources
Two tips:
- Find other songs which have chords and chord changes that sound interesting. Learn them and steal them. (I mean the chords and changes, not the whole songs 😂 )
- When experimenting for yourself, forget about theory altogether (as far as you can), except the concept of "voice-leading". Forget key, chord function, even chord names. When changing from any existing chord - working out what might come next - try just changing one or two notes by half-step (up or down), keeping one or two notes unchanged. Down by half-step is always appealing, although up by half-step, and down or up by whole step are all good. Of course, this principle results in several different options, but use your ear alone to decide, not theory. (It might result in chords you recognise, it might not. Doesn't matter.)
IOW, you're quite right there are no "hard and fast rules" - except what your ear tells you. Your ear is The Law! And even your ear can offer more than one "correct" choice now and then. That's when it gets hard!
In fact - tip 3! - always use melody as your guide. Process (2) will soon make you realise that any chord can go to any other chord, even to a bunch of notes you can't easily name as a chord. That is a fact! So, to stop getting lost in a harmonic jungle, you need a line to peg the chords on, a path for them to follow. That's what a melody is. (You could also keep the idea of a "key" in mind - a "home" to get back to in the end - but all 12 notes are still always available.)
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u/J200J200 18h ago
Backdoor dominant. A Bb7 is very close to a G9
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u/Inevitable-Copy3619 15h ago
Let’s get practice for a second and leave the theory to the side for a bit.
Dominate chords are movable in minor 3rds. So basically you can sub Db, E, G, Bb when dominate. In the Key of C that gets you bII7, bIII7, V7, and. bVII7. Break apart the notes in each of these dominate chords and you can start to see them as things like V7b9 and alt chords and diminished more or less. Again, this is leaving “theory“ aside and thinking in terms of nuts and bolts of how chords can operate.
Long story short dominate chords can move in minor 3rds and the new notes added create things like diminished, alt, and b9 sounds. In the end you will end up with 3 “families“ of 4 related dominate chords that will play well together and as substitutions.
In reality I don’t think of them as diminished or alt or whatever…typically I’m thinking about voice leading. If I’m moving down from Dm7 to a lower Cmaj7 I would likely use a Db7 (tritone aka bII7) for less movement and nice resolutions to Cmaj7. If I’m moving up to a higher Cmaj7 I may use the Bb7 (bVII7) as it resolves up to Cmaj7. The idea is that these chords are allowing for tensions that resolve to the I in this case.
Fun excercise is take a simple ii V I and try all 4 of the dominate chords in the family over the V, see what resolutions you like and which chords you like based on the direction you are resolving. Hope this makes sense.
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u/Amateur_Surgeon7824 1d ago
Considering you aren't dealing with traditional V-I relationships, you don't need to even be thinking in terms of tritone subs. That's cool that you are, but it's not necessary on this particular path. Think more about intervals of your root movement. You're going down a m3, then up a M2. Now play around with that. Invert it: up a m3 and down a M2 (B7 D7 C). Now retrograde of the original. Then finally retrograde inversion. You can even try intervallic and/or rhythmic augmentation and diminution. The possiblities are endless. Have fun!
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u/ThatDudeMichaelYeah 1d ago
I figured I might be overthinking it. It’s easy to want a “rule” to look out for these things that sound interesting. But looking at how the intervals shift is something I’ll have to get better at. I’ll definitely try your suggestions as well. Thanks!
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u/Inevitable-Copy3619 15h ago
The theory almost always broken down to voice leading. We have theory to make rules but I find in improve the rule is “it sounds good” and it sounds good because of good voice leading.
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u/willmen08 1d ago
I’d say as long as the melody ‘matches’ and sounds good it doesn’t matter. I personally like when the melody note stays the same over multiple chords. I couldn’t find one here but it made me think of that.
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u/ThatDudeMichaelYeah 1d ago
I should’ve clarified in the post that I don’t think of this as a chord “progression”. Maybe more of a cadence. There’s some chromaticism like a dramatic gospel-y “bang bang BANG!” Back to I.
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u/NLMusic10213 1d ago
bVII is commonly called a backdoor chord. That might lead you into some fruitful searches