The Rev obtained his first pair of drum sticks at the age of five, and received his own drum set at the age of ten. In just one year, he was playing The Black Page with college students in a percussion ensemble conducted by his teacher. He had always kept up with his lessons and six years later, in high school, he started playing in bands. Before leaving to join Avenged Sevenfold as one of the band's founding members, Sullivan was the drummer for the third wave ska band Suburban Legends. At the age of eighteen he recorded his first album with Avenged Sevenfold titled "Sounding the Seventh Trumpet". His early influences included Frank Zappaand King Crimson. The Rev admitted in a Modern Drummer Magazine interview that "I was raised on that stuff as much as rock and metal.".
Later on in his life he was influenced by drummers Vinnie Paul, Mike Portnoy, Lars Ulrich, andTerry Bozzio. He even had a "visual influence", Tommy Lee, on which he commented that "I never thought I’d have one of those." Sullivan's signature ability which he called “‘the double-ride thing,’ just for lack of a better definition, because no one does it,” is a technique that can be heard on the track "Almost Easy" in which he doubles up at a fast tempo between the double bass and ride cymbals. In a recent DRUM! magazine transcription of “Crossroads”, The Rev revealed to the name of the trick as the "Double Octopus." Drumming CompanyDrum Workshop endorsed the Rev and said he could have any drum set he wanted, so he chose a double bass drum set, which he preferred over a double bass pedal.
The Rev didn't only play the drums, he was a vocalist, songwriter, and pianist for Avenged Sevenfold as well. His skill as a pianist can be heard on the track "Warmness on the Soul" where his piano part is the main focus of the song which includes a solo written by the Rev. His vocals are featured in Avenged Sevenfold's “A Little Piece of Heaven”,“ Brompton Cocktail”," Critical Acclaim" “Gunslinger”, “Lost”, and “Afterlife." He used his knowledge of the guitar and piano to write the songs "Almost Easy", "A Little Piece of Heaven", "Afterlife" and "Brompton Cocktail" that appear on Avenged Sevenfold's self-titled album. He also contributed to the making of "Critical Acclaim" and "Lost".
The Rev's vocals will be present in the new album Nightmare. According to M. Shadows, the Rev sang in key in the demo and there was no bleed in the microphone so they were able to put it on the record; expected to appear in the song "Fiction". Jimmy wrote the song (originally entitled "Death") and handed it in to M. Shadows and said that this was to be his final song for the record, he passed away three days later.