The Husumer Orgelbuch closes with a group of three pieces by that most illustrious of baroque composers, Anonymous :-)
This is a Concerto in A Minor. Unlike the other concertos in the book, which are consistently in fast-slow-fast form, this concerto opens with an Adagio movement. It is followed by a Vivace, a second Adagio movement, and a closing Allegro in 12/8 time.