So when you're playing a few pieces (prelude, offering, postlude) in church, and the music director says that one of the hymns is Eternal Father, but you don't have your descant books with you, how can you add value? I really wanted to because the service was August 5, August 4 is the Coast Guard's birthday, and Eternal Father is the official hymn of the Coast Guard and Navy.
So I played the melody on the 1st and 3rd verses, and then for a pseudo descant I used the tenor line. It works pretty well for many tenor lines, so it can be a good way to step in unprepared if the need arises.