I know nothing about Viktor Patrik Vretblad except for his dates: (5 April 1876 — 15 January 1953).
This is a relatively brief, chromatic, and highly expressive work.
It serves to demonstrate the Clarinette stop of the Choir.
Since the Schulze Clarinette is not under expression, using the swell pedal to "express the accompaniment" helps somewhat to create the impression of dynamic variance.
The work is dedicated to Gustaf Haag, who was the Organist of St. Klara's Church in Stockholm.
The score is attached below, as well as a photo of Patrik Vretblad and a photo of St. Clara's Church in Stockholm.