[mjg2]

as a programmer and a classically trained pianist, this section:

> For example, the notes C, E and G (The C major chord) can have any of the following names, based on what is considered to be the root note.

> root note chord name

> C C Major

> E E Minor #5

> G G sus4 (13)

> (To the best of my knowledge, I'm no music theorist)

is disqualifying for any usefulness in this program-- it will lead to more misguidance than clarity. without theory, there is no reason.

i would analyze these inversion chords in the frame of the key of C major: CM, C6, and C64 based on Figured Base Notation https://en.wikipedia.org/wiki/Inversion_(music)#Figured_bass

[epcoa]

For what it is worth it’s not wrong to say that the triad where E is the root would be Em#5. The inversions you point out still have the same root (C) even if the bass is different. But I agree you’ve identified the fundamental problem: we cannot infer the root note and, therefore the name (enharmonics aside), from just a set of notes and attempting to is a fool’s errand. Even with a root note, it's going to be difficult many times to have a sensible answer

The key problem with this implementation in addition to not simply taking the root note as input (or a key or scale), appears to be the chord database is pretty spartan, since it doesn't appear it would identify C-E-G as anything other than CMaj. If you want figured bass/slash notation then you'll need to specify that as well (bass note).

A number of chord namers take these as additional inputs.

[tunesmith]

Em #5 would have a B#, not a C. This isn't a pedantic point; it very much matters if we're trying to be accurate with chord naming.

Another example to illustrate how identifying the root is important: C E G A. It's either a C6 or an amin7.

[kazinator]

E-C is simply not a sharp fifth. Sharp fifth is enharmonic with minor sixth. E-C is a major sixth.

[recursive]

Interesting.

Coming from a cover band/local small-time musician, C6 means C-E-G-A. In other words, C with an added 6 on top.

The charts I play from generally don't have any inversion information on them, and I probably play different inversions each time.

[epcoa]

This is unfortunately one of the ambiguities in notation. But usually not a problem because it should be quite clear when figured bass is being used.

In jazz/pop notation inversions are indicated with slash chords.