With the melody in the bass line, what do you call these chords?

Question

Here's an example of some chords.

The two higher notes can be considered a C (power-) chord, i.e. root and fifth only.

A very lazy interpretation and notation could therefore be C/A, C/B, C, C/F.

However, when the chords are considered inversions and rearranged with a closer voicing, as shown in grey, the chords could also be called Am7 (no fifth), Cmaj7 (no third), C and F9 (no third).

Note: Fadd9 appears to be a better name for the last chord, because there is no seventh, and if there was, it would be an E, i.e. a major seventh.

As many notes are omitted, often even the third, no matter how you put it, the chords remain somewhat ambiguous. I'd like to learn about some reasons how they might be called. Maybe other interpretations are possible as well?

https://music.stackexchange.com/a/64763/65475 suggests that the notation [Chord]/[Note] is commonly used for non-harmonic bass notes, i.e. notes that would otherwise not make sense in the context of the chord.

Answer 1

The posted chord names don't make sense to me, unless there is more music that we are not aware of. OP may have private harmonic considerations, e.g., something in their ears that we can't hear, which may mitigate the usefulness of the rest of this answer. We'll see....

How Else Might These Chords Be Named?

Seeing F9, I am expecting that chord to be going somewhere, but where? This would usually be heading to some type of Bb chord (there are a few other slightly more exotic usual suspects), but there is no Bb present among the other chords; maybe that is yet to come. Further, F9 contains an Eb, which is also not among any of the presented notes. An Fadd9 could make sense here, since the notes of that chord are F, C, and G, i.e., the root, fifth, and ninth of Fadd9. There is some ambiguity since there is no third here.

The first chord is plausibly Am7 with A, C, and G, the root, third, and seventh of that chord. This is all you need to convincingly voice a seventh chord; in fact seventh chord voicings containing only the root, third, and seventh are so useful and common that they have a name: shell voicings. Let's grant that the first chord is Am7, then.

Calling the second chord CMaj7 seems problematic. The notes here are B, C, and G. If it were a CMaj7, the third is missing; this in itself is not a deal-breaker. The major 7th is in the bass of the chord, which is a little unusual, but not unheard of, and again not a deal-breaker. I suppose that it would be fine to call this CMaj7, but thinking of the chords that way makes the chords seem more static than they are when I play through the actual voicings as written. Instead, I am tempted to call the second chord a G, or maybe better, a G11. The written voicing has the root, third, and eleventh of this chord.

The third chord contains E, C, and G, so calling it C seems natural.

Given the above, I would be tempted to write the progression as Am7 G11 C Fadd9. That is, in roman numerals: vi7 V I IV. Now the IV chord, the Fadd9 might go back to the I chord, which seems kind of natural to me since I think that C sounds like the tonic here.

Pedal Points

It is more common to find minor chords with 11ths than it is to find major chords with 11ths; this is because the third and fourth of a major chord are only a half-step apart, i.e., the 11th is a minor ninth above the major third. This sound isn't always appealing, but sometimes it works very nicely. In the posted music the top two notes C and G are maintained throughout, making them pedal points. Pedal points are usually in the bass, but they don't have to be. This actually helps mitigate the dissonance of the G11 chord by placing that minor 9th in a larger context; pedal point passages often temporarily admit some dissonance. Viewed as a pedal point, the C is first the minor third of Am7, then the 11th of G11 (a dissonance), then the root of the C, and finally the fifth of Fadd9.

Wrap Up

So I would, at least as a start, think of these chords as Am7 G11 C Fadd9, and if I were looking for other notes to flesh things out I might use the notes of those chords to guide my thinking.

Incidentally, when I played the posted music I was immediately reminded of this tune by The Shins that was popular several years ago.

Answer 2

C5/A, C5/B, C5/E, C5/F

I don't think your "lazy interpretation" is lazy at all. It's succinct. There's no need to over-complicate things. Analysis isn't about being clever; it's about conveying information. The best analysis is the one that conveys the relevent information most efficiently.

Note that you forgot to specify the bass note E in the 3rd chord. I've included it.

Also, I've chosen to specify that the chord is C5, not C major. Remember that unless it is indicated otherwise, a triad is assumed to be major. While C major isn't necessarily wrong, I think it is misleading if the context is a power chord with a melody underneath it.

It is very common to encounter notes in a melody which are not members of the current chord. Most melodies will contain such nonchord tones. It is a mistake to think that the harmony must be reinterpreted when a nonchord tone is encountered. This is true regardless of which voice the melody is in.

In general, the naming of chords should take the chord's function into consideration. This principle is most clearly demonstrated with examples of chords that are enharmonically equivalent but are spelled differently because of how they behave (eg a dominant 7th chord vs a German augmented 6th chord). An interpretation such as Am7, Cmaj7, C, F9 requires more justification. Extended chords usually have some sort of implied function and expected resolutions. If none of those expectations are met, such an interpretation seems inappropriate.

Analysis should also take the aural effect into consideration. Do you actually hear this as 4 different chords? Probably not.