I was there!
The reason the Andantes [[and male background singers in some cases) were used was not dramatic at all. Lamont Dozier liked to arrange and record the backgrounds last in order to fill out gaps in energy left by the musicians and lead singer. Canceling gigs that had been booked months earlier just to put a little icing on a record was an extremely expensive proposition for the company and, most of all, for the artists themselves. The Andantes were on a lot more records than the ones mentioned for that simple workflow and economic reason.
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