Outside of Grace Slick, They are the best female vocalists whoever graced the planet. my favorite female vocalist is Vera Lynn, who had a string of hits from 1936 through 1954. In May, she celebrated her 91st birthday. One of my favorite female singing groups is The "That Girl" Quartet, who recorded "Nightingale" in 1911.
I vaguely remember Vera Lynn, having worked at a WNEW clone in he late ‘60’s. But I'm ignorant of the 1911 group. But I don't doubt you. Beautiful voices are timeless.