We know for a fact that that vocal is NOT LaBrenda Ben. The latter has a much deeper voice, with a very different tonal quality. I, myself, may be the erroneous source of the rumour that that artist is LaBrenda Ben. We taped that off a Jobete Music acetate in the late 1970s, for potential use in the "From The Vaults" album series. It was never used. We never found out who it was. I had played that cut for several collectors I had known (including our own "Modern Soul Sucks"). I remember saying (in jest) to one of them, "Maybe it's LaBrenda Ben?", knowing, full well, that it couldn't possibly be her. I had no incling that anyone might take that comment seriously. Whoever it was probably forgot the context of that conversation, and connected that name with the cut.
Rod, I guess you can vouch for my "sense of humour" being so deadpan, that no one could possibly tell when i'm kidding! The artist may have just been a demo singer, with The Andantes behind, or an unknown group trying out on a Jobete song, but who were never signed, or maybe an early Velvelettes' cut (but certainly not Cal on lead, or one of their more recognisable voices).