It is unclear when and under what circumstances Straube met Heinrich Reimann. It seems likely the connection was made over the younger man's regular attendance at concerts of the Philharmonic, which Reimann served as organist and program-note writer. Probably reproducing Straube's own conflicting recollections made at different points in his life, Wolgast put the date at 1888, Fischer at 1892. Like Dienel, Reimann had come to Berlin from elsewhere, the former as a student in 1863, the latter as a grammar school teacher in 1879 and, after time away, again in 1887. Reimann had come from Catholic Lower Silesia, an area with eighteenth-century ties to Prussia, absorbed into the new Reich in 1871. Son of the prolific church music composer Ignaz Reimann, he had earned a philology degree at Breslau in 1875, laying the foundations for a career as a serious writer on musical topics from Byzantium to Brahms. He likewise had studied organ playing with the Breslau cathedral organist, composer, and Royal Music Director Moritz Brosig, himself a writer on historical Catholic music. By the time Reimann moved permanently to Berlin in 1887, he had converted to Protestantism, no doubt largely under patriotic fervor for the new imperial culture. When Straube crossed paths with him shortly thereafter, Reimann's extraordinarily varied career was in ascendancy as a composer, critic, organist, and librarian at the Staatsbibliothek, where he would become a curator in 1893, and where he equally could have met the young man. For a brief time thereafter, he taught organ and theory at the new Klindworth-Schaarwenka Conservatory, where Straube's piano teacher Leipholz served on faculty.
As an organist, Reimann stood at least superficially in Dienel's camp, positioned against conservative voices like Haupt—organ professor and later director of the Berlin Church Music Institute, and probably teacher to Johannes Straube during his time there—and Salamon Kümmerle, both of whom cautioned against the newfangled technologies and shallow effects of the “modern organ.” The Schlag Philharmonie organ of 1888, over which Reimann presided as organist to the orchestra through late 1896, and on which Straube perhaps had lessons with him, generally would have suited his purposes, with its two Swell chambers, electropneumatic action, variable wind pressures, a proliferation of registration aids, and more.