How would you analyze this chord progression and the function of Am7 here?

Question

Disclaimer: Novice songwriter here.

I've started to write a new song, started with a 16 bar funky bass line in C natural minor and kept adding some chords which I think might not be fully correct but sounded good to my ears :

Cmaj7 - Bbmaj7 - Abmaj7 - Bb maj7 
Cmaj7 - Bbmaj7 - Abmaj7 - **Am7** 

I have two questions and please forgive my lack of experience in advance :

1. Removing the Am7 at the end, does that chord progression makes sense at all?
2. What's the function of Am7 here? I like to have it there since it generates a gentile surprise and doesn't give the thing listener would expect.

And lastly, I am open to any external source/book recommendations.

Thank you all.

Answer 1

First let me say if you’re composing a piece it’s up to you to decide if is sounds good or not and up to your listeners to decide if they like it so don’t concern yourself too much with “correct“ with the exceptions of errors in the writing and performance.

One question before I answer yours, you mentioned your song is in C natural minor but this chord progression is in C major. Is this a section of your song where you changed key to C major or is the song actually in C major?

Answers:

1. These chords are often combined in different ways so yes it makes sense with or without the Am7 at the end. Offhand, the ending vamp of “Beginnings” by Chicago uses a similar chord progression, minus the Am7 and in a different key.

2. Going by this being in key of C major the function of the of Am7 is a VIm7, the relative minor of C. The Bbmaj7 is a bVIImaj7 and the Abmaj7 is a bVImaj7. These two chords are not native to C major but are often used chords borrowed from two parallel minor modes. the Bbmaj7 comes from the C Dorian mode and the Abmaj7 comes from the C Aeolian, or natural minor. Kudos to Chris P for catching an inaccuracy in my answer over 3 years later, lol!

Answer 2

'Function' normally refers to a chord progression where tensions are set up and resolved. Where one chord is likely to have a dominant-tonic relationship with the next. 'Cycle of 5ths' stuff.

This isn't that sort of harmony. It establishes C as a tonic, purely by being shaped round a regular return to C. The other chords have no particular harmonic relationship to C other than being 'not C'. I can NAME them in relation to C major - Imaj7, ♭VIImaj7, ♭VImaj7 etc - but those are just labels, not functions. G7 has a functional relationship to C, there's a dominant-tonic pull. B♭maj7 doesn't (other that its afore-mentioned 'not C' attribute).

Chords of the same type 'go' well together. Particularly if they are adjacent to each other. Yours satisfy both criteria. They're all maj7 chords, their roots walk down and up a scale (but not, you'll have observed, the scale of C major, as might have been expected). The name for this sort of thing is 'planing'.

Now, you're looking for validation of the Am7 :-) I can't really grant you any. There's no 'rule' that looks at your first 7 chords and suggests that Am7 might be a 'correct' place to go. It's next door to the preceding chord. It's the same harmonic density as the other chords (a triad is 3-density, a 7th 4-density, a 9th 5-density... mixing chords of different density can sound unsatisfying). But those are just a lack of reasons against it, not reasons TO use it.

Some would say the Am7 DOESN'T fit. It certainly doesn't follow the pattern set up by what came before it. But why should it?

What does your song do next? Back to the beginning, another round of Cmaj7, B♭maj7, A♭maj7... Or does the Am7 lead off somewhere else? Then, we COULD start thinking of 'function'. The string of maj7 chords could be analysed as a decorated tonic, an elaboration of Cmaj7. Where could that Am7 lead? My ears like Gmaj7. Then, perhaps, Am7, Bm7, Am7... a G-based section. NOW we've got something to analyse in a functional way, perhaps?

Answer 3

I assume this is a 8 bar idea that repeats after bar 8.

"Function" is a loaded word in music theory. The is formal harmonic function which is essentially a framework of harmonic progression moving through categorical types of chords, chord functions: pre-dominant, dominant, tonic. Sometimes chord symbols with Roman numerals are used to represent the chords like ii6 V7 I.

Let's skip over some analysis and just point out that your chord progression does not use those functional categories. Not a problem, we just look at the chords in other ways. You could analyze dissonance and consonance and chord qualities (like major versus minor.) You could also analyze linear aspects and voice leading.

The first thing I noticed was all your chord roots move by step. That's very linear. The line goes down two steps then back up making a smooth undulation.

Second I noticed that almost all the chords are the same quality. They are all maj7. Diatonic chords don't do that, so this is chromatic harmony. I think maj7 chord have a bright, pretty sound. They can sound mellow, kind of drifting around without a (functional) goal. If you played this progression with a samba rhythm it will probably sound like Antonio Carlos Jobim! Anyway, your basic palette is bright & colorful, and the feel is potentially laidback.

The Am7 at the end is the concern.

Aesthetically you could describe this in endless ways. It's a surprise. It's a question, etc. etc. I think an objective thing you can say is provides a break in harmony that potentially could become too static. Placing it at the end of the progression I think really works. Objectively is demarks the boundaries of the progression. That gives it shape. Aesthetically, is like a someone is daydreaming and suddenly at Am7 thinks "maybe I will... " and then upon repeating and returning to the original chords they say "...on second thought, maybe I won't." Replace that with any narrative you like. The point is something happens at the end of the progression, but it doesn't take up a new idea, it returns to the opening idea.

From a voice leading perspective something noteworthy happens with Abmaj7 to Am7. Cmaj7 Bbmaj7 Abmaj7 all involve all the voices moving. (In this context "voices" just mean the tones of the chord.) But with Abmaj7 to Am7 two of the voices change - Ab and Eb move up to A natural and E natural - but two voices C and G don't change between the two chords. Also, that step upward of the root at bars 7 to 8 mirrors the same step upward at bars 3 to 4. The kind of symmetry is another good way to give form to the progression when functional harmony is not determining form.

When the whole progression repeats there is another important thing to point out about the Am7. It is the relative minor of C major. Relative major/minor pairs have a sort of shared musical identity. Traditionally the idea is they come from the same key, but when comparing just the chords they share similar tones. Cmaj7 is C E G B and Am7 is A C E G. They differ by only one tone, three of the tones are shared C E G.

If we considered this music to be in C, Cmaj7 is the tonic and Am7 is the submediant. There is a certain idea in music theory that the submediant can act as a sort of alternative tonic. I don't think that's really the theory we want to apply, but it does sort of support the idea that Am7 isn't so strange here. It's a kind of direct link back to Cmaj7. Regardless of that theory it's easy enough to see that with 3 out of 4 tones shared it's a smooth transition from Am7 to Cmaj7.

I put it in notation to better see some of the voice leading stuff...

...I used ties to show the shared voices. I don't mean to literally hold those tones, the ties are just to show the notes are common tones between chords.

Also, with the first chord change I had the top voices move in the opposite direction of the bass. I did that to set up a smooth step-wise move back from Bbmaj7 to Cmaj7. Blue arrows highlight that motion. You don't have to do that, but it is common to arrange the voice leading my smooth steps this way when the chords move chromatically through non-functional chords.

Answer 4

Since you developed the bassline first, it is important to know on which note the chords are being played - they would actually change name if played over a C or over a Eb or over a G, for instance.

Re progression "making sense": the first 3 chords are just planing parallel downwards, that is coherent and you do not need special theory frameworks to "justify" that. Notice how no diatonic scale features two (let alone three) adjacent maj7 chords, that's why it sounds "interesting".

The Am7 gives chromatic tension, because it sits between Ab and Bb. You can say it has "dominant" function, because the surprise it generates leads back to the beginning of the sequence.

TL;DR I wouldn't use functional analysis to look at funky music, you'll end up with too many convoluted explanations for things that usually come up from player's fingers without much thinking (and to great musical result!).