Rob,

You could also try Bb6/C (which is equivalent to Gm7/C but BIAB might interpret Bb6 a little differently from Gm7) Interestingly, the notes you give C-F-Bb-D-G do correspond to Csus9 since there is no 'E' (or 3rd) in the chord.

What I often do in situations like this to reduce the chord to its base triad and see if that works. Then, when I discover what the chord's base is, I add appropriate extensions like 7, 9, 11, etc.

Base triads that I'd try for this chord are C, Csus, Bb, Gm.

Regards,
Noel


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