As biographical subjects go, Dieterich Buxtehude (ca. 1637–1707) was not so kind to historians: few contemporary documents detailing his life survive, only a small number of his works can be dated, he published little relative to his known output, and most manuscripts in his hand were lost by 1750. Consequently, Buxtehude-related scholarship tends to center less on Buxtehude himself than on better-documented peripheral aspects, such as his known influence on J. S. Bach. Most historians also assume his purely Lutheran identification based on his high-profile organ job at the most distinguished Lutheran church in Lubeck, a major center of Hanseatic power.

Certain emerging details about Buxtehude's life, however, complicate exclusively Lutheran impressions of his religious and intellectual proclivities. Most recently, in 2018 Olga Gero traced the previously unidentified text of Buxtehude's cantata Fallax mundus (BuxWV 28) to a Flemish Jesuit emblem book, Anton II Wierix's Cor Iesu amanti sacrvm (Antwerp, ca. 1585/6). This adds to a growing list of works, including a Pange lingua and Salve desiderium incorporating Marian texts, that appear strangely “un-Lutheran” for a musician of Buxtehude's social prominence, employed by an especially high-profile Lutheran church in a major center of Hanseatic power. A few scholars, such as Martin Geck, reconcile such contradictions with theories about Buxtehude's affiliation with the German Pietist movement. While it is true that Buxtehude drew many texts from Pietist or Pietist-leaning authors (including John Rist, Angelus Silesius, Heinrich Muller, Thomas Fritzsch, and Johann Wilhelm Petersen), Kerala Snyder and Joyce Irwin have argued that a cornerstone of the seventeenth-century Pietist movement was a drive to ban from the church service many of the same compositional genres that form the majority of Buxtehude's known works. The latest reexaminations of Pietism's sociological roots, however, reopen questions about Buxtehude's contact with the movement. For example, Tanya Kevorkian now convincingly dispels modern notions of a unified seventeenth-century Pietist identity on sociopolitical grounds, citing major economic—and as a result significant artistic, consumerist, and theological—disparities between Pietist practices in Lubeck and those in other parts of Germany.

Recognizing a growing opportunity for subtlety within this vibrant discussion, this chapter offers a new perspective on Buxtehude's mystical-musical intentions—involving numerical theology, alchemy, and ultimately Rosicrucianism—based on evidence in his compositional process and members of his innermost circle of friends: theorist Andreas Werckmeister and composer Johann Theile.