Lucia di Lammermoor.

Despite what you may read on IMDb and elsewhere, Enrico Caruso does not appear in this film though it was mimed to a recording by Caruso. Mendel’s system utilized prerecorded commercial recordings of famous artists lip-synched by look-alike actors during film shooting. The music is the sextet Chi mi frena in tal momento from Act Two of Gaetano Donizetti's opera Lucia di Lammermoor which premiered in 1835.