The albums The Divine Wings of Tragedy and V: The New Mythology Suite were partially recorded in The Dungeon, Romeo's home studio.

[2][3] In April 1994, a new version of The Dark Chapter, which featured Romeo and keyboard player Michael Pinnella, was released by Zero Corporation.

[3] When asked by Zero Corporation if he had a band in the same genre,[1][2] Romeo recruited bassist Thomas Miller, drummer Jason Rullo, and vocalist Rod Tyler, with Pinella remaining on keys.

"[3] The album was positively received, with AllMusic praising Romeo's "pyrotechnic displays" and describing Pinella and Miller as "equally competent on their respective instruments".

Following the initial run of Japanese shows, bassist Miller and drummer Walling both left the band due to their unwillingness to tour.

[14] In 2005 Symphony X was featured on Gigantour, a summer festival headlined by Megadeth with Dream Theater, Nevermore and Anthrax.

Two Symphony X songs from the tour, "Inferno" and "Of Sins and Shadows", are featured on the Gigantour DVD and CD-set, released in September 2006.

The recording process was delayed numerous times due to water damage in The Dungeon, as well as an extended touring cycle.

[19] A limited number of albums from certain vendors contained a special DVD, which consists of footage of the band's live performances.

[20] Paradise Lost debuted at number 123 on the Billboard 200 album chart in the United States, selling 6,300 copies in its first week.

[23] The band also revealed plans to perform in Japan and other Asian countries, as well as appear for the first time ever in Russia, India, and the Middle East.

"[30] On February 25, 2011, Symphony X played the first show of their 2011 tour in Stuttgart, Germany, where they performed two songs from the upcoming Iconoclast: "End of Innocence" and "Dehumanized".

Iconoclast debuted at number 76 on the Billboard 200 album chart in the United States, selling more than 7,300 copies in its first week.

[34] Rullo spent a week in hospital before being released home to undergo a rehabilitation program that would take 3–6 months under doctors' care.

[34] John Macaluso joined the band on tour for their South American and European dates, giving Rullo time to recover.

[36] He also stated all lyrics and instrumental tracks were composed and ready to be brought together, and that the album would be less heavy than Iconoclast: "If I had to compare, I would say that it's a combination of The Odyssey and Paradise Lost — something in there.

[26] According to singer Russell Allen, the band entered a short hiatus during 2017 in which they did not perform, due in part to his commitment to Adrenaline Mob,[42] although it was announced during a January 2018 interview with Metal Nation that the band had plans to get together in the following months and begin writing a follow-up to Underworld.

[43] On July 14, 2017, Adrenaline Mob was involved in a serious vehicular accident, which resulted in severe injuries for Allen and the death of the band's bassist and their tour manager.

[49] During bassist LePond's May 2020 interview with Metal Nation when asked about plans for him and the band, he had confirmed that the band was ready to start writing the tenth studio album, a follow-up to their 2015 album, Underworld as soon as the virus slowed down, and that writing would begin in about "a month or so".

In a November 2022 interview, Romeo reiterated that work was continuing but that the band had not yet settled on a theme or vision for the record.

[14] In a 2024 interview with Ola Englund, Romeo again confirmed that the band have been working on new material between legs of their American and European tours.

[55] Symphony X's music includes complex timings and odd meters while incorporating elements of heavy metal and progressive rock.

[56] Their early albums in particular contain strong neo-classical elements reminiscent of Yngwie Malmsteen, Randy Rhoads, and others.

Symphony X is often compared to other progressive metal bands such as Dream Theater, Fates Warning, and Shadow Gallery.

[66] Keyboardist Michael Pinnella released a solo album, entitled Enter by the Twelfth Gate, on October 12, 2004.