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I am wondering how to assess the following modulation from C major to Bb major according to rules of traditional harmony:

chord progression including C/E D7 F Bb modulation

I threw the modulation together without thinking about it much, and thought "that'll do", but I want to dig deeper. For context, I'm doing a pop song on piano sort of composition. The song was feeling repetitive, so I wanted to add a bridge that could provide a bit of a break from the otherwise repeating chord progression: I-vi-I-V

I want the transition into the new key to be smooth, so I understand the use of a pivot chord--a chord shared by both keys--would be advisable. D minor and F major are shared by both keys, and, as you can see, I employ the F major chord before the B flat (tonic) arrives. But I know that among the most effective pivot chords are those that would normally lead into the V chord of the new key, such as II and V, but F major is the V chord in Bb major.

Also, I don't know why I chose the D7 chord to precede the F major, because it has a non-diatonic note (the F#).

Basically, I'm lost. I would like to continue working on this modulation, if it makes sense. But I am also happy to totally scrap it if there is a better way to go.

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    I'm unclear on your question: there seem to be several. Are you asking if the D7 is okay to use? Are you asking how to get back to C major in m. 17? And right at the end you ask about I5-6; what is that referring to? – Aaron May 11 at 2:55
  • Thanks @Aaron. The question has been edited--hopefully it's a little more clear. – 286642 May 11 at 3:47
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    That does help; however, it seems there are two distinct questions. Are you intending to relate them? If yes, the relationship needs clarification; if no, I suggest you open the Aldwell and Schachter question as a separate issue. As written the two questions deserve very different answers. – Aaron May 11 at 3:51
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In traditional terms, the D7 is unusual, but you aren't breaking any rules, and in a pop setting especially, it works well.

A formal analysis seems like overkill here, but an informal one might be helpful. Imagine you were planning a modulation to G minor rather than B♭ major. In that case, your Amin -> C/E -> D7 -> F would be interpreted as ii -> IV -> V -> ♭VII. Now consider that G minor is the relative minor to B♭ major. Recognizing that, your modulation could be understood as a sort of deceptive cadence.

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  • As a suggestion, try replacing the first Bb chord with Eb, and see if you like it. Analytically, this would make a deceptive cadence in G minor, but the Eb chord is also IV of Bb, so to my ear it smooths the transition a bit. If you like it, the first Bb of the second pair (m. 13) could also be Eb or stay as is. – Aaron May 11 at 4:29
  • The D7 to F progression is breaking common practice period harmony rules. Even though they tolerate chromatic mediants, it's only with much reservation, and the major-minor 7th chord is found only as V7, VII7, or a re-spelled augmented 6th chord (so all secondary dominants and pivot chords must follow conventions for resolving those, and I really don't think that D7 is resolved properly). If I listened to music with that chord progression, I'm pretty likely to throw it in the 20th-21st century soundtrack music camp. – Dekkadeci May 11 at 12:17
  • @Dekkadeci Thanks. Is there a chord you would suggest trying in place of the D7 that would work (according to rules of traditional harmony)? – 286642 May 11 at 22:31
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    @286642 C minor would be the most straightforward choice, but I disagree with Dekkadeci's assessment, as he leaves out common-tone chords and the more liberal voice-leading permitted as common-practice harmony became more chromatic. The G minor progression in my answer also covers you tradition-wise, as would adding in the Eb chord, which would make it a true deceptive cadence in G minor while also serving as a pivot to Bb. – Aaron May 11 at 22:45
  • @Aaron thank you very much – 286642 May 12 at 2:11
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That F chord is much more than a pivot chord. Of course it works as such, but it happens to be the dominant of the new key - B♭. That's a very common ploy to make way into a new key. I guess that the majority of folk who hear a dominant chord, (or a dominant seventh chord), would expect its tonic to follow.It's what dominants do!

Taking things a little further, you could use ii-V-I into the new key. Cm(7) - F7 - B♭. That Cm in key C (major) is also a pivot chord, and works equally well.

As far as the D7 is concerned, it's a common chord used in key C. It's the V/V, although here it moves directly to IV - a sort of interrupted cadence, if you like. But it could be a herald to Gm, which happens to be the relative minr of the target key - B♭.

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your modulation works fine: It is built by 5 phrases of 2x2 bars. I'd bring them in this order:

bars

1-4: C - C/E - Am C - G7

5-8: C - C/B - Am C/E - D F

9-12: Bb - Bb - F/A - F/A

13-16:Bb - Bb - F/A - G

17-20: C - C/E - Am C - G7

Am C/E could be understood as vi-vi34 (egc ~ am7) leading to D (circle of fifths)

D can be considered as a secondary dominant V/V, resolving in a suspension (F ~ bVII of G)

F becomes dominant of Bb. The second 8 bars in Bb are properly in Bb even there is no subdominant Eb in view.

leading back to the repetition of the 1st phrase (which could be also the beginning of verse 2)

(I've tried to sing a melody using only the triads of your chords, it sounds nice: like dodo somi domi so ... )

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  • Thank you. does it matter that Am -> D is going backwards in the circle of fifths? Does that make this a retrogression and therefore stall the sense of progression? – 286642 May 11 at 17:09
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    Am-D is a ii-V progression, one of the most usual, like subdominant - dominant. And the progressions are in general counter clockwise. – Albrecht Hügli May 11 at 21:42
  • Secondary dominants go counterclockwise ("backwards") through the c.o.f. (5th-fall progression), any if we replace a V7 by its minor parallel we have ii-V7 chain. – Albrecht Hügli May 12 at 11:34
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The next phase in this kind of composing method would be adding a melody, but you don't mention melody at all. Melody lines can be very important in whether a modulation feels smooth or not.

A song in C could well have the chords D7 - F - Bb somewhere. What matters is, where and how the chord changes are rhythmically, and what the melody does. For example, sing Mary Had a Little Lamb in C over C - D7 - F - Bb. Maybe a bit funny, but in C, the melody is able to keep it in C.

A song in Bb could well have the chords D7 - F - Bb somewhere. What matters is, where and how the chord changes are rhythmically, and what the melody does. For example, sing Mary Had a Little Lamb in Bb over Bb - D7 - F - Bb. Maybe a bit funny, but in Bb, the melody is able to keep it in Bb.

So, overlay a melody line over the chords, something in Bb. Forget about the previous key, don't look at it, cut or hide it away. Write a melody line over "D7 - F - Bb", thinking about Bb all the time. Then join the "in C" and "in Bb" parts back together. Do you like it? If not, adjust the joining-together melody notes. Maybe use similar phrases in both keys, or a continuous ascending or descending motion that starts from the previous key and continues over to the next key.

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  • I think "Mary Had a Little Lamb" in C over C - D7 - F - Bb is going nowhere. Which chords correspond with which parts of the melody? I tried singing the last 2 measures over the Bb chord and the overemphasis of C clashed with the Bb chord; I tried changing chords every 2 quarter notes (assuming "Mary Had a Little Lamb" starts with 2 8th notes) and the overemphasis of E over the D7 chord similarly clashed too hard. – Dekkadeci May 11 at 12:22
  • @Dekkadeci In C the melody notes are E D C D E E E D D D E G G. It would go like this: (C) Mary had a (D7) little lamb, (F) little lamb, (Bb) little lamb. And then for example, resolve back home to C major, the tonic went nowhere from C. This works great. Over the Bb, the melody adds a #11 and a 13. On the D7, the melody makes it a D9. On the F the melody makes it an F6. This is a completely plausible melody that directs the feeling of tonic to C, and when played in Bb: D C Bb C D D D C C C D F F, the melody directs the same chords to Bb tonic. – piiperi Reinstate Monica May 11 at 12:26
  • Or actually, in Bb the chords would be Bb - D7 - F - Bb, and in C they would be C - D7 - F - Bb. But the point was redirecting the chord sequence D7 - F - Bb to different tonics by using melody lines. The OP doesn't mention melody at all, even though melody can be a total make-it or break-it decider. – piiperi Reinstate Monica May 11 at 12:33
  • I think we'll have to agree to disagree about how well "Mary Had a Little Lamb" in C works over that chord progression. I personally find that the melody adding a #11 and a 13 over the Bb chord sounds terrible. – Dekkadeci May 11 at 12:38
  • @Dekkadeci You'll get used to the taste! ;) LOL Have you tasted Japanese natto? I can already almost stand the smell after 25 years. The first time I nearly fainted. – piiperi Reinstate Monica May 11 at 12:45

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