The recently posted question "What chord is Dm7 with a Bb?” asks:
If I have a Dm7 chord played on the 5th fret of a guitar as a barre chord and move my pinky to play the Bb note next to the A on the 4th string I have the notes
D Bb C F A
so basically a Dm7 with an added Bb. Can someone please tell me the name of this chord?...
It initially occurred to me, as a semi-literate musician, that a simple answer might be that it’s an augmented minor 7th chord, as the Bb would be a raised 5th. No answers from more studied theorists here arrived at this, so I searched around a bit and found that conventional theory seems to say that there is no such thing as an augmented minor chord.
As a case in point, in the answers to that question there seems to be some consensus around this being a BbMaj9/D, or something similarly notated, against which I have no authority to argue. But with theory being meant to explain what’s happening in music, it seems to me that it would be less complicated and more direct to call it a Dm7+. It’s rooted on D, has a flat 3rd, a flat 7th, and a sharp 5th. Contextually it’s preceded by Dm, and followed by F (according to comments from OP.) But if augmented minor chords are not valid, then I suppose it’s necessary to explain the chord some other way, like calling it a BbMaj9/D. Perhaps there are more foundational elements of theory which, in my semi-literateness, I am not aware of, and which invalidate augmented minor chords. Someone please enlighten me!
To summarize: Why do augmented minor chords not exist as a valid part of chord theory and notation?