Although this was possible for castrati because of the hormonal imbalance following castration, Maniaci claims that, for some unknown reason, his larynx did not develop and lengthen completely during puberty, causing his voice not to "break" in the usual manner.
Maniaci claims that this physical particularity has given him the ability to sing in the soprano register without sounding like a typical countertenor or a female singer.
During his early teens, his family relocated to Western Pennsylvania and resided in Peters Township, a small community located approximately twenty miles south of Pittsburgh.
In the 2001–2002 season, Maniaci made his Carnegie Hall debut in Chichester Psalms with The Orchestra of St. Luke's, sang Nerone in L'Incoronazione di Poppea for Toronto's Opéra Atélier, and the title role in Xerxes with Wolf Trap Opera.
In 2004, Maniaci portrayed the role of Cherubino in Wolfgang Amadeus Mozart's The Marriage of Figaro with Pittsburgh Opera.
In 2007, he made his debut with Opera North as Atis in The Fortunes of King Croesus and with La Fenice in the role of Armando in Giacomo Meyerbeer's Il crociato in Egitto.
[1] Also in 2007, Maniaci returned to Glimmerglass Opera to perform the title role in Gluck's Orfeo ed Euridice.
In 2011, Maniaci played the role of Sesto, alongside Measha Brueggergosman as Vitellia, in Opera Atelier's production of La Clemenza di Tito in Toronto, Canada.