As one of my primary interests is improvisation, I am always looking for ways to include improvisation in the liturgy. Here is a responsorial psalm built over a simple two-chord progression. The refrain melody is composed to fit over the chords, and while there are verses written out in the score, the cantor (as demonstrated here) is free to improvise the melody for each of the verses.
This video was recorded at the Easter Vigil which begins in darkness, so the lighting is very dim. Sadly, my iPhone ran out of memory, so I am only able to share the first verse here.
The music for this composition is included in the Feasts and Solemnities volume of the Audubon Park Psalter.