The Polyphone attachment was the invention of Chicago businessmen Leon Douglass and Henry Babson, both giants in the early phonograph industry. The Polyphone was patented by Douglass in 1890 as a method of increasing volume. The idea was simple: using 2 reproducers set approx. 1/2" apart running in the same groove would effectively double the volume. This solution is effective. Of course one result is twice the wear on the early soft brown wax cylinders.

Closeup of the original Polyphone attachment.

The Polyphone attachment, 2 horns, carrying case were offered at $12. By 1902 the Polyphone was obsolete with the introduction of Gold-Moulded cylinder records.