Here's a clip from 1987 of Libbi singing "I Know a Man Who Can." Libbi started singing with her siblings in 1970. She is the only original Perrys member still in the group.
Now let's take a look at Libbi from August 2013. This was taken in Branson at Silver Dollar City.
While things may have changed from 1987, it's clear that Libbi was and will remain one of the top alto singers of the genre.