He is a childhood friend of Manowar singer Eric Adams. DeMaio played bass in several school bands. In the 1970s he toured with the musical Godspell (premiere in 1971 in New York City), taking musical lessons with the conductor. He worked as a pyro-tech for Black Sabbath during their “Heaven and Hell” tour. He is known to display his technical abilities and playing speed during solos both on Manowar studio recordings and live shows, often covering classical parts such as “Flight of the Bumblebee”, which DeMaio has retitled “Sting of the Bumblebee” in reference to his high-speed renditions of the piece.
In 2006, shortly after creating the record label Magic Circle Music, he became manager of the Italian metal band Rhapsody of Fire. He is also a producer for the band HolyHell.