A curious chord progression, and a particularly curious chord. Why does it sound great?

Question

I have been wondering about this chord progression ever since I happened across it. I am a relative newcomer in the established theory community, so I'm not sure if the question I will come to ask here has an obvious answer or not.

C - Am - G - Dm | C - B♭ - Dm - Fsus2 | Fm6 - C - Dm - Am | G - F - C - G

Here's an example including a melody: https://soundcloud.com/mlnvs/curious-prog/s-4S9AqdEkLDR

Now, some of the progression is pretty bland. It sounds pretty C major, but seems to suddenly modulate to D minor with a simple B♭ major triad. I'm very curious about the C major to B♭ major transition and why exactly it sounds so good. I, as many do, love the sound of the "VI i" chord change in a minor key, but it's not about that.What sounds lovely in this situation to me is the transition from that C root chord to the B♭ chord.

When the second Am chord happens in the third group of four chords, it feels very resolved, almost as if the key were actually A minor for a moment. I'm wondering if my ears are enjoying the B♭ because it's the Phrygian II chord in Am. But then why would it sound so great coming from a clearly resolved C major chord? I really don't have a clue and would love any insight into this. Thank you very much (in advance) to anyone taking the time to respond.

Answer 1

It's hardly a curious or rare type of sequence! The ♭VII chord does get played quite a lot. Whilst it's not diatonic - which seems to befuddle a lot on this site, it's still a commonly used chord.

Some say it's a borrowed chord from the parallel minor key. In C minor, the VII chord is B♭. Others regard it as a sort of dominant chord to the tonic. It could even be seen as the IV chord in IV's key. A bit like V/V, but the opposite way - IV/IV. The Beatles used sequences which used ♭VII in more than a few of their songs.

What we can't do is explain why it sounds great to you. Apart from possibly 'it's non diatonic, so it creates a bit of a surprise'. Which it shouldn't!

Answer 2

Like you said, the B♭ chord creates a temporary feeling of perhaps being in the key of F. The introduction of the B♭ note triggers a re-thinking or re-consideration or re-calibration of the harmony in your mind, and to many people it is a good feeling. You can do a roughly equivalent thing by playing a Gm chord instead of B♭.

A similar change but towards the key of G is done by playing a D major chord. C - D - G. And then back with the reverse action, G - F - C. The C - D - G movement is so commonly used that the D chord has been given its own name: "secondary dominant". The name is much fancier than the actual thing.

This loops between feelings of C and G majors: C - D - G - F (repeat)

This loops between feelings of C and F majors: C - B♭ - F - G (repeat)

The B♭ chord doesn't necessarily have to lead towards F major. It's just an out-of-scale thing and it sets your thinking process in motion. "What's happening now?"

Move towards Eb: C - B♭ - E♭

Move towards Dm: C - B♭ - A - Dm

Move towards E: C - B♭ - A♭ - F# - E (chain of similar things)

Move towards Gm: C - B♭ - E♭ - D - Gm

Introduce an out-of-scale note and make the listener re-think the harmony. This has many names, "borrowing" and "modal interchange". If the tonic i.e. home note seems to move permanently and not temporarily, then it's a "modulation". It just feels nice to most people. Why? Who knows. Why do things usually fall towards the earth and not away from it? It's a law of nature. For the vast majority of people it is enough to accept that as a law of nature, and learning about gravity adds nothing. Things just fall down, not up. Call that "gravity" if you need that for social acceptance or something. Hey you need to talk proper language so people won't think you're uncivilized, which would jeopardize your status as a respected member of your community. :)

Any 2-year old knows how gravity works and has no problem accepting it. In a sense your question is equivalent to "why do things move towards the floor when I release them from my hand". Or maybe, why is it fun to throw things around? Toy around with music like a toddler plays with toys, and you'll learn how stuff works. :) This StackExchange is explaining gravity to toddlers by reading them scientific articles from Newton and Einstein, when the toddlers should be given toys. Not "modal interchange" mumbo jumbo.

So what I'm saying is, there are two separate things: (1) What happens harmonically = temporary feeling of possible key or mode change. The OP already figured this out through experimentation. Excellent! (2) Why does it feel good? Now THAT cannot be taught by explaining, it just feels good and that's it, it has to be experienced. Any possible "explanation" using lower-level phenomena is going to be useless rubbish with the primary purpose of satisfying a Western logic-information-knowledge valuing person's need to feel that everything is in scientific control. The OP must be given MORE TOYS to learn that there are many similar temporary changes and that they just feel good.

Answer 3

The unusual here is the progression rather than the chord: B♭ in an Am context is, in tonal harmony, a very common chord (known as Neapolitan chord). But in these cases it is found acting as a substitute for IV, leading to V-I, usually in minor mode. I know a few examples of b-flat after C chord (you hear it right in the opening of Mozart KV 493 and Bach BWV 815, both in E-flat Major, so the actual note is d-flat), but it is not the whole B♭ chord, just the note b-flat to make the I7 chord and then IV-V-I.

Answer 4

This is a curious chord progression, I would like to hear it it context. The Bb chord in the key of C is not that curious though, it is a non-diatonic bVII chord used widely in pop and jazz. Some would debate me bit I consider it a chord borrowed from the parallel minor. I recently read and commented on a question that already had a great answer by @DonHosek and was based on this particular chord. There is a lot of useful information and a few links there, here it is:

Backdoor cadences - what would be the ♭VII chord in A major?

As for your comment regarding the Am chord, even though you’re right about the bii Phrygian reference those two chords are too far apart in the progression to try and establish a relationship between them in my opinion.

Answer 5

The I - bVII movement is a leftover from the Mixolydian mode so it can be viewed as diatonic. The rest is more or less self explanatory. The whole piece sounds very dorian to me