In Sousa's diatribe against soulless machine-generated music, he seems to imply that the machine does not record… it recreates. In recorded music, he saw the return of the enslavement of music by the "mathematical and mechanical." He references the rebellion against "musical automatics" in the 15th and 16th centuries, offering Palestrina and Luther as exemplars of advocacy for the emotional and soulful in music. The implication is that the polyphony of the 14th century and before was not expressive and soulful… but I won't follow that rabbit trail.
My point is that Sousa conflates the concepts of "recorded music" and "machine-made music." He writes, "the ingenuity of a phonograph's mechanism may incite the inventive genius to its improvement, but I could not imagine that a performance by it would ever inspire embryonic Mendelssohns, Beethovens, Mozarts, and Wagners…" Notice that he refers to the playing of a record is a "phonograph performance." Sousa did not consider the phonograph to a conduit, but a robotic musical performer that threatened to make the human performer obsolete. We may dismiss his opinions as the ranting of an alarmist (or as Joe suggested, greedy) composer, but his concern for the future of amateur music-making parallels those of ethnomusicologists who note that western art music is (perhaps increasingly) dominated by a strict divide between musician and non-musician. It is possible that recording has managed to make this line more distinct, and to put more individuals in the rigid category of "non-musician" or "audience." As recording has improved, no one must learn to play Beethoven piano sonatas in order to have them "performed" in the home. We have sound systems built into our living rooms so that we can simply connect our devices and have a home filled with whatever music we would like to hear. These recordings, of course, are made by virtuosic, "professional" performers, and we are content to let them do the music making in a recording studio, producing a static performance that we can enjoy as often as we want.
I found it interesting that Sousa connected the rise of listenership with the disappearance of amateurs and educators: "… without the slow process of acquiring a technic, it will be simply a question of time when the amateur disappears entirely, and with him a host of vocal and instrumental teachers, who will be without a field or calling."
I agree that amateur music making has been on the decline (at least, "amateur music making" in the most traditional sense) for a long time, that there is a deepening divide between musician and non-musician, and perhaps that recorded music has acted as a catalyst for these phenomena during the 20th century. I'm still skeptical, though, because I'm not sure that the role of the amateur music maker was ever really to "fill our homes with music." Do parents have their children take piano lessons because they enjoy hearing their child pound out finger dexterity exercises? Perhaps this is a cynical point of view, but my understanding is that piano lessons and musical training became popular because of middle-class bourgeois sensibilities. Sousa writes specifically about the girls who make music in the home, cautioning that we should not "let the mechanical music-maker be generally introduced into the homes" because "hour for hour these same girls will listen to the machine's performance, and, sure as can be, lose finally all interest in technical study." Of course, he fails to recognize that many of those girls were given piano lessons simply because of the societal value of being "musically trained." Some of these girls would become quite accomplished; few would have careers as musicians. As I said, the view of amateur music that I've just presented is informed by politics; Sousa was trying to point to an inherent moral good in making music. "Singing will no longer be a fine accomplishment," he laments. "Then what of the national throat? Will it not weaken? What of the national chest? Will it not shrink?" I can't help but find these comments ironic, since at this time, the "national voice" was technically only that of its white males… but that's a separate issue.