I just found these videos featuring the Antrim Mennonite Choir on YouTube, and they are so lovely I just had to share.
How beautiful that they sing the original versions of these old hymns, not as they were later edited. This version of Rock of Ages is the one I remember growing up in the Howard-Miami Mennonite Church.
I found the album, Amazing Grace, and additional albums by this choir at Scroll Publishing Company. Amazing Grace includes 18 hymns and is on sale, so it's well worth the price. What a blessing to find these!