This is a paraphrase by Anthony G. Petti of Verbum supernum prodiens by St Thomas Aquinas.
In CWB I it is set to MELCOMBE by Samuel Webbe. This tune has been used to set dozens of texts, but I can’t find anywhere apart from CWB I using it for this text.
1 Dear Saviour, victim for our sins, to lead us to eternal life:
Protect and guard us in your grace, and keep us from all earthly strife.
2 To your great name be endless praise, O ever blessed Trinity,
We pray you, grant us perfect life with you throughout eternity.
This is an example of organ music that is impossible to sing with:
That tune is the one that everyone sings the O Salutaris at Benediction. It’s one of the Australian quirks of music. I don’t think anyone is going to try learning the plainsong melody for it like they did the Tantum Ergo. Since O Salutaris is actually the end bit of Verbum Supernum, it makes sense why they chose the melody.
The video is a very good demonstration of one of the types of ludes that organists like to play. It could be a prelude, postlude, interlude, hymnlude, or otherlude. Those organists enjoy showing off their fancy expensive organs, loudly and proudly, usually because they know that they do it well.
The creative hymn addict can manage to sing loud enough for the organist to give in, but I haven’t tried it yet as I have to play the part of one of those little obedient “angels” that serve on the altar.