This package includes separate files for alto 1 and alto 2 in the Prologo and Act 3. In the Prologo, the differences are only in Fiesco's aria (the first minute or so of the recording). In Act 3, the differences are in a passage for women's voices in 4-part harmony. In acts 1 and 2 the altos never divide. (That said, if you need a recording where altos go to the middle voice in three-part splits, please get in contact.)