How well did Sousa know Pepper?

My guess is that when Sousa reached out to Pepper in 1892, asking the instrument maker to build him a modified helicon bass for use in his band, the two knew each other fairly well. Here's what we know for sure that supports such speculation:

• Sousa moved to Philadelphia in 1876 - the same year that Pepper started his music business in that city. Sousa was 21, and Pepper was 23.
• Sousa was based there for the next four years, working as a musician, composer, arranger, and conductor.
• He even worked for a couple of (other!) Philadelphia music publishers for part of that time - W. F. Shaw and J. M. Stoddart.
• On July 20, 1879, Pepper published the first of eleven Sousa marches, "Globe and Eagle":

• On December 30, 1879, Sousa married Jane van Middlesworth Bellis of Philadelphia (was Pepper perhaps at the wedding?!)
• After becoming the director of the Marine Band in late 1880, Sousa went on to have Pepper publish more of his works, including the marches, "Guide Right" (Mar. 14, 1881), and "Resumption" (Sept. 14, 1882).
• On Dec. 30, 1882, Pepper published the Sousa operetta, "Desiree," which had a three week run in Philadelphia in 1884 (did Pepper attend a performance?):

• On June 8, 1883, Pepper published the Sousa marches, "Bonnie Annie Laurie," "Mother Goose," "Pet of the Petticoats," "Right Left," and "Transit of Venus."
• Almost 10 years went by before Pepper published his next Sousa march, "Triton" (Oct. 10, 1892) - even though Sousa had written 22 marches (including "Semper Fidelis" and "The Washington Post"), and many other compositions, during that time.
• However, it was earlier that year (1892), shortly before Sousa left his post as the director of the Marine Band in order to start his new civilian band, that Sousa gave Pepper the idea for the modified helicon bass.
• On May 24, 1893, Pepper published the Sousa march, "Esprit de Corps" (originally written in 1878).
• On April 3, 1895, Pepper published the Sousa march, "Right Forward" (originally written back in 1881).
• The original Sousaphone was built by Pepper at some point that year (1895), and was taken on tour by the Sousa Band for the first part of 1896.
• Sousa gave concerts at the Academy of Music in Philadelphia multiple times from the late 1880s to the late 1890s (first with the Marine Band, and then with his own band), when the Pepper building was just six blocks down the road (did Pepper come to some of those concerts?).
• On August 13, 1896, Pepper re-published the Sousa march, "Transit of Venus" (and yes, the image of Sousa on the cover below is the exact one we see engraved on the bell of the Pepper Sousaphone):

• In late 1896 and early 1897, Pepper re-published six Sousa marches, all written years earlier, in a piano arrangement:

However well Sousa and Pepper may have known each other, it appears that 1897 was the last year that Sousa used Pepper as a publisher. Further, starting in 1898, Sousa favored instruments built by C. G. Conn, and especially the Conn Sousaphone. And from that point on, I am aware of only one time that Sousa mentions Pepper, and that is in a newspaper interview in 1922, where Sousa notes that Pepper built and named the very first "Sousaphone."

[Most of the above facts are taken from Patrick Warfield, Making the March King: John Philip Sousa's Washington Years 1854-1893 (Univ. of Illinois Press, 2013); and two works by Paul Bierley: John Philip Sousa: American Phenomenon, Second Edition (Warner Bros. Publications, 2001) and John Philip Sousa: A Descriptive Catalog of His Works (Univ. of Illinois Press, 1973). The above images of Pepper publications are all available for download at the Library of Congress website]