Among his early musical influences were Elvis Presley, Jerry Lee Lewis, Little Richard, Buddy Holly, and Ritchie Valens.

By the early 1990s, influenced by the Beatles, he began songwriting, as well as recording on a 16-track reel-to-reel studio he had assembled in the basement of his house.

During the summer of 2000, Castellano studied advanced digital recording techniques and audio engineering at Wave Studio in Staten Island, under the instruction of Ron Thal.

In December 2003, Castellano served as sound engineer on Blue Öyster Cult's 13 city tour of Germany.

He first performed with Blue Öyster Cult as bass guitarist in Las Vegas, Nevada on September 18, 2004,[7] shortly after Danny Miranda left the band.

[3] In addition to performing with Blue Öyster Cult, he also plays guitar in the band Morning Starlett with his ex-wife Ann Marie.

He frequently works with Andy Ascolese, and released an album of power pop titled 2 Part Invention in 2005.

In 2011, Castellano had a viral video hit with his rendition of Queen's "Bohemian Rhapsody" where he performed all of the vocals and instrumentals.

[11] They toured together again in 2024 & 2025 [12] and Jon Anderson released a new album True in August 2024 on Frontiers Music featuring the Band Geeks.