What key and why does this work?

[LdV]

Hi, I recently created a chord progression that sounds good to my ears, but seems like it has a borrowed chord from the parallel Major as well as a chord that doesn't make any sense but sounds good.

Can you please help me work out why this works?

The chord progression:
Cm7/9 - F#aug#7/#9 - Dm7/9 - Cmaj7/9

[BertKoor]

F#aug#7/#9

This is a weird one. A regular augmented chord can go under three names: F#Aug, BbAug (or AbAug) and DAug have the same notes. Mixed in with an F and a G# (not Gb with Ab?) it gets a bit crowded.
Perhaps it helps if you spell out fully the notes you play.

[jancivil]

I can more or less devise an analysis by a bit of a stretch.

C Eb G Bb D
? [Gb Bb D F A]
D F A C E
C E G B D

in C [minor]: i7(9) or ii7(9) of Bb. (EDIT: there was a 7 attached to that Bb, brain fart)
III7#9 of Eb harmonic minor
ii7 (9) of C major
I7(9)

OK, we may be tonicizing the 3rd degree of C minor through Bb, Eb's dominant, itself tonicized for one moment but eliding I. (note my ‘?’* ie., de facto Ebm^7?)
ii - I of C will will not be very abrupt from there.

there's nothing wrong with that, but the progression as I'm trying to justify tonally isn't so conventional.
I am supposing your "doesn't make sense" is the augmented triad (M7), which is symmetrically 3 things at the same time. Diatonically this construct forms at the 3rd degree of harmonic minor.

without hearing it, this is going to be guesswork. But, there's a certain sense I found with some thought.
NB: there are things in the music of Erik Satie as odd as this. It could be pretty hip. At least ther's food for thought…

[jancivil]

Edit: changed my mind, there’s enough C to come away with ‘it’s in C’.

it gets a bit crowded.

not necessarily, not at all. Voicing determines that, not note choices.
We can devise chords of "all" 12 tones that are quite lush, in fact.
Frank Zappa's Chord Bible is founded on vertical constructs of 7 to 12 note scales, for example.
This one is a mere 9th chord

I'm not seeing any necessity indicated for close voicings. The OP reads "why does it work", not "suggest to me how it doesn't".

[jsaras]

You don't have to try to jam this progression into a "key-centered" jail. Each root is its own gravity.

I don't know how you voiced the chords or what voice-leading you used, but this progression easily lends itself to each note moving by step, so it's not going to trip anyone's alarms.

[losangeles]

The augmented F# chord likely somewhat fulfills the role of a subdominant- although more dissonant due to the augmented intervals. Resolving to the minor second and finally to the tonic likely provided soothing relief.

[jancivil]

The Gb augmented chord may also be seen congruent with if not the selfsame as Eb minor/major 7. I don’t get how this particular sound is subdominant at all.
We have essentially a shift to an Eb area from C minor.

Gb is subdominant to Db, which doesn’t occur here. Even as a general tone area in a more expansive view, that’s awfully tense to be that sound.

[terriandralph]

Not sure if this is an interpretation of the chord progression that is way out in left field somewhere, but for what it's worth...

I kind of took jancivil's comment to heart that, "without hearing it, this is going to be guesswork", so when I played the progression, to my ears it sounded like the Cmaj7/9 chord wants to go somewhere, so when I followed the Cmaj7/9 chord with an F major chord I figured my ear was hearing the Cmaj7/9 chord as a V chord.

I decided to check out all of the notes of the chords in the example, and they all have a connection to the F major/minor tonalities:

Cm7/9 - minor v7/9 chord from F minor;
F#aug#7/#9 - I interpreted this chord as a Neapolitan maj7#5#9 chord with the notes of the chord being spelled Gb, Bb, D, F, A;
Dm7/9 - minor vi7/9 chord from F major;
Cmaj7/9 - V maj7/9 chord from F major.

[KBSoundSmith]

Seems to me the Root Progression is C - Bb - D - C. Here is a quick realization, in root position for all chords:

Chord Progression 001.png

https://app.box.com/s/tmm49v7yt75bm8s4wqprje972545el55

My reasoning was based upon looking to see if there are fifths within the chord and if so, how many and which fifth (if multiple) is lower than the other. While in the second chord the Gb, Bb and D do indeed spell an augmented triad, more essential is the Bb - D - F - A, where the Gb is an addition to the seventh chord.

If one insists upon Roman numerals and pretends they're just triads for a second, just to focus on the Root Progression (and because I don't want to think too hard about the spelling, haha), then you get the following: i - bVII - ii - I

[NKF]

If you strip it down

The Faugmented can work as a D7#5,
Then bird blues type going from a dominant to the minor 7 which well ii7 is pretty much IV and IVs , well any chord I guess but in particular those all kinda work in a plagal setting when you have shared voices between each chord.

I mean it works if you voice it properly. I will say I do feel strange using tre qualifier works. Working depends on the genre and the harmonic bandwidth you have to work with.

[EatMe]

Analysis of the chords:
- Cm7/9 = C Eb G Bb D - in C minor
- Bbmin7/maj7 = Gb Bb D F A (is a chord from the Bb blues scale) - in C minor with added A, modal to C major
- Dm7/9 = D F A C E - in C major
- Cmaj7/9 = C E G B D - in C major

This may sound very well to the ear, as it used a chromatic change from minor to major.

[jancivil]

I kind of took jancivil's comment to heart that, "without hearing it, this is going to be guesswork", so when I played the progression, to my ears it sounded like the Cmaj7/9 chord wants to go somewhere, so when I followed the Cmaj7/9 chord with an F major chord I figured my ear was hearing the Cmaj7/9 chord as a V chord.

I decided to check out all of the notes of the chords in the example, and they all have a connection to the F major/minor tonalities:

except it begins and ends on a C chord of one or another type, with nothing landing on F
Word to the wise: a maj7 is never a V chord in tonal music; which is defined by a dominant/tonic relation {where V7 = dominant seventh aka major/minor 7 chord.} I find major 7/maj9 a very stable object. I also don't reckon C^7 as very friendly to 'F major/minor tonalities'. nudge nudge F Lydian.
So at this point I don't trust that.

BUT*
alright, Cm7/9 - F#aug#7/#9 - Dm7/9 - Cmaj7/9 is what's given
Now, I'm interpreting chord #2 as an F# augmented triad with a ^7 and #9. Here I may be correcting to my idea of a viable harmony on "F#": Gb Bb D F A. I wasn't advised to the contrary by LdV so (they seemed to vacate, you can blame me)

If it's F# - E (Gb - Fb) instead, it could be looked at as a secondary dominant: V7 of B (Cb). Or b5 substitute for dominant, bII7 *of F.

One opinion was it's easy to say D7#5. D F# A#. The argument following that was pure word salad, but sure it could be. given a Gx or A ("#9") originally gets us a hard weirdness from there (two types of fifth) so a hard no.

it doesn't have to make sense in normal terms if the author digs it. I think my relating the 'wrong' chord to Eb (out of C minor) is the better 'food for thought' at the end of the day as it were.

[jancivil]

but the first part of the sentence (what key?) in the OP can't really be answered. We'd almost surely need more music (before it or following it). IE: Dm7 to C^7 ≠ strong resolution. There is music where strong harmonic movement isn't the point at all, but the questioned chord on F#/Gb gives the lie to it being real placid-like.

[BertKoor]

but the first part of the sentence (what key?) in the OP can't really be answered. We'd almost surely need more music (before it or following it).

... which likely won't happen. This was the OP's first & last post ever.

[BertKoor]

Can you please help me work out why this works?

Do you really care? Please post back then...