The cord progression for the song is:

Dmaj7, Am7, Gmaj7, Bbmaj7

And the melody is mostly from Dmaj pentatonic. So the song appears to be in D major.

My question, how does Am7 work here? Since it's the 5 cord of D major, shouldn't A7 be the correct diatonic chord choice? Playing A7 sounds good, but my confusion is why Amin7 doesn't sound dissonant?

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    Play Dmaj7, D7, Gmaj7 ... sounds super dissonant? :) No. The Am7 has the C note, which makes it perform a part of the role of a D7. And Am7 - D7 - G is a two-five-one into G. – piiperi Reinstate Monica Mar 17 at 20:56
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    You can substitute or "prefix" many seventh chords with a minor chord that has the original chord's seventh as its third. For example if you see C7, you can substitute it with just a Gm or Gm7, or a combination Gm-C7. The logic is that for example C7-F is a basic five-one motion, and you can "boost" it by making it a two-five-one. In your example, the booster chord Am7 is used alone and the D7 is left out. It's just a trick, "borrowing" stuff from what you normally have in the key of G major. Bmaj7 is interesting too, but you don't ask about that? :) – piiperi Reinstate Monica Mar 17 at 21:43
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    Bitonicity, perhaps? D major and G major in a loop? – user45266 Mar 18 at 0:43
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    Bbmaj7 is another borrowing trick, alternating between D major and D minor feelings. It's almost the same as using a Gm in a D major key context, as opposed to G major you'd normally have as IV chord. Alternate between D and Bbmaj7 - whenever you're on the D chord, solo stuff from D major or D lydian or whatever D majorish scale, and whenever you're on Bbmaj7, solo stuff from e.g. D natural minor scale. Wax on, wax off, ... major, minor, ... It's one of the most basic things in jazzy harmony and it also corresponds to a tonic shift of 3 semitones up/down, so D major <-> F major (i.e. D minor). – piiperi Reinstate Monica Mar 18 at 9:42
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    @MichaelCurtis Initially I had Amaj7 instead of A7. I corrected this later and added a comment. The question was why are we playing Am7 instead of A7. Hopefully this clarifies things. – SivaDotRender Mar 19 at 4:06

The change is effectively from D to G, with the questionable chord being the transition.

Often, that D will have its ♭7 added (C), making it into D7. Sometimes, M9 is also added, (E), making the chord now D9.

Let's look at the make-up of Am7: A C E G. Compare with D9: D F♯ A C E. Several notes the same in each - namely A C and E. That could explain it.

Another is also a well used sequence - D>C>G. Here, the transition chord is C. Again, C E G are all contained within Am7.

You state that A7 is the diatonic A chord in key D. Correct. But that isn't going to help get to G. A7 works best pushing things back to D, as it's the dominant seventh, and that's sort of its role. That wouldn't work, as we're already on D, and need to move to G, not D again. Changing its make-up and swapping C♯ to C♮ does that.

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  • I selected this as the answer because it contains a combination of all the answers above. – SivaDotRender Mar 18 at 15:38

Rarely, if ever, the question of "why does this sound good/bad" can be answered once and for all, as it will always be subjective to some extent.

So, let me just offer one way of looking at it, and see if it makes sense to you.

So, try this:

  1. Temporarily replace the Am7 with Cmaj7 (i.e. its relative major chord). Your sequence now becomes D, C, G, Bb. (All maj7 chords). Play that a few times...

  2. Temporarily drop the maj7 of the chords, i.e. make all chords plain triads. Play D, C, G, Bb a few times as plain triads...

In this way you have "dumbed down" the progression to its most elementary form.

Actually you can go one step further, replacing the major chords with power chords, i.e. just root and fifth. Try that as well...

Anyway, now that you have this "primary colors" version of the progression in your ears, go back to the original progression (with the Cmaj chord). Play that a few times, and compare the plain triads version with the maj7 version...

And finally, go back to the initial version, with the Am7.

In other words, one way to look at this progression, and to understand why it flows in that particular way, is to consider it as a common D-C-G-Bb progression, to which some color has been added in the form of maj7 notes, and in one case, replacing a major chord with its relative minor.

Can you hear the maj7 version as an "expanded" or "colorized" version of the plain triads?

As I said, that's just one way to look at it, but perhaps it helps...

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  • Thats and interesting way to look at it. The progression definitely sounds like a more colourful version of D, C, G, Bb. Could you also explain the role of Bb since its not in the key of either Dmaj or Gmaj? – SivaDotRender Mar 18 at 4:33
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    @SivaDotRender I hear the Bb chord as a passage chord which creates a bit of "bluesy" tension at the end of the loop. Using the same method in the answer above, try this: play the sequence D-C-G-A (all major triads) a few times (i.e. changing Bb to A), and note how that sounds. Then play it D-C-G-Bb (all major triads). Notice how using Bb instead of A adds some spice. And I feel that "rock-blues" flavour, I think is caused by the out-of-scale (passage) minor third (G-Bb) interval used, rather than a more "square" classical G-A or G-C that could have been used instead. – MMazzon Mar 18 at 11:47

One more explanation for this chord - this loop progression can actually be viewed as an example of bitonicity: shifting between two key centers at regular intervals.

The loop is

Dmaj7 Am7 Gmaj7 B♭maj7

. The two keys being shifted between are D major and G major.

  • We start with Dmaj7, an obvious indicator of D Ionian.
  • We then move to Am7, which is where the shift starts to occur. Dmaj7 and Am7 do not exist in the same key, but Am7 does serve as the ii of G major. This move can be thought of as similar to a secondary dominant, but using the jazz analogue of ii-V-I progressions. Here, there is no V chord, moving directly from ii-I.
  • Gmaj7 seems to be our second main key center, and it is followed by B♭maj7.
  • B♭maj7 does not exist in the keys of D major or G major, but it serves two interesting roles in the progression. With respect to G major, B♭ is a chromatic mediant of G, so it sounds kind of refreshing, and the maj7 quality helps to set the ethereal mood. With respect to D major, B♭maj7 is the ♭VImaj7 chord. This could theoretically be explained as a chromatic mediant, but it is also a clear example of modal interchange - borrowing a chord from a related mode (D minor, here). This ♭VI sound is common enough that on repetition it becomes obvious that this chord falls back down to Dmaj7 with a strong leading tendency.

This is a very R&B-influenced progression. It's also possible to view the whole progression from the perspective of D major, using modal interchange to explain both Am7 and B♭maj7. However, when we land on Gmaj7 the progression feels resolved enough to justify designating G as a sort of secondary tonic in the loop. Besides, in a strictly functional viewpoint, Gmaj7 should be the IVmaj7 chord of D, but it doesn't ever really fulfill that predominant role in the loop at all.

I'll be honest: this concept of bitonicity is pretty new to me, so I'm not an expert at using it for analysis yet, but to me this is one of the more clear-cut examples of the use of this tool in understanding how harmony can achieve a composer's goals. I think this concept has a lot of potential in furthering our understanding of how popular music works.

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