It's interesting that after 52 posts in this thread, and probably upwards of 100 performers mentioned, by my count there are exactly 0 female groups and 2 female soloists mentioned (Connie Francis, Joni James), and exactly 1 mixed group that had prominent female members (Fleetwood Mac). And there are 0 classical recordings.
I don't know what all of that signifies, if anything, but the statistics certainly seem striking.
Regards,
-- Al