As I have mentioned before, I sometimes cantor in St Patrick's Cathedral at the 1pm Mass (regularly on Fridays, but other times on occasion). This afternoon we had Psalm 93 (or Psalm 92 in the old money), with the refrain "The Lord is King; He is robed in majesty". It isn't always easy to find a setting for the week day psalms, and when I do, I don't always like them. So I often make one up.
When making up music for the antiphon, it has to be catchy enough for the crowd to catch on one hearing (especially where there is no accompaniment). I believe that the best rule for this is if the music imitates the rhythm and pitch at which the spoken voice would speak the line. Saying the antiphon over and over to yourself you can usually hear the "tune" behind it.
Here is the way I sang this psalm this afternoon. You will get what I mean.