Detailed biography: James Duff Brown, Ed., Biographical Dictionary of Musicians with a Bibliography of English Writings (A. Gardner, 1886), page 539. (Gives name rather more sensibly as Hermann, which was probably the composer's birthname. "Herrman" was - probably - used by composer or publisher to make the name stand out on scores.) Middle initial also appears as G.
Also a critic and the publisher of Saroni’s Musical Times, several times referred to (as saber-toothed, in her introduction, page 8) in Lawrence's edition of George Strong (1820–75)'s several volumes of musical diaries (e.g. in Strong on Music: Reverberations, 1850-1856.)