The tune for the hymn is "Italian Hymn," and this is the second phrase:
In the fourth verse, the text here is "Glorious Trinity," and "Trinity" is sung with a melisma. The first syllable is sung to three notes, which - to some degree - represents the Trinity. There are three notes for one syllable, in a similar manner to how the Trinity is "three distinct persons in one divine being" (to quote Luther's Small Catechism).
I'm a bit out of my depth with the theology, though, hence the "to some degree" and "similar." I don't think this is a perfect representation, but it's something of an illustration.
