Among the gems that I found while at the U. S. Marine Band Library (just over a year ago) that were not directly related to Sousaphone history was this explanation of how to pronounce Sousa's name - written by Sousa himself:
This was in Sousa Band Press Book no. 8, and is a clipping from the April 23, 1899 edition of the New York Journal. Here's the accompanying article:
I'm not entirely sure what the "good old-fashioned way" of pronouncing it was back then, but today we tend to say "Sue-zuh," and "Sue-zuh-phone." But I guess it should be "Sue-sar" and "Sue-sar-phone"!