It seems there might be a bit of confusion in your statement. "The Moldau" is actually a symphonic poem composed by Bedřich Smetana, not a church composer. Smetana is well-known for his nationalistic music that relates to the Czech landscapes and culture, and "The Moldau" (originally titled "Vltava") is a musical representation of the Vltava River in the Czech Republic.
This piece is an example of program music, which is instrumental music that tells a story or paints a scene. In "The Moldau," Smetana depicts various scenes along the river, such as the sound of the water, the hunting of a group of nymphs, and the bustling activity of a village along the banks.