The Dassing brothers first began experimenting with music by the means of more traditional rock music instruments, such as guitar and drums. By the time the two formed their first band with vocalist Rich Mendez, Benestrophe, the instruments of choice became synthesizers and samplers. Most of the two tapes worth of material they recorded subsequently became available as the releases Auric Fires and Sensory Deprivation on RAS DVA records. After parting ways with Mendez, the two brothers began work as Mentallo and the Fixer. Their very first release No Rest for the Wicked saw a limited 500-copy run on vinyl by the Portuguese label Simbiose records, and also gained the attention of Talla 2XLC from Zoth Ommog records.

Mentallo and the Fixer soon after began their long-term relationship with the American industrial music record label Metropolis Records with their second release Revelations 23. This release solidified the band's sound, which included "snarling distorted vocals, hard cutting sequencer rhythms, and a thunderous beat". However, Mentallo and the Fixer changed directions with their following release, Where Angels Fear to Tread, an album which was more heavily influenced by gothic music.

At this time, in 1994, the Dassing brothers formed a side project with vocalist Michael Greene called Mainesthai. Mainesthai's two releases, Out to Lunch and Mentallo and the Fixer Meets Mainesthai were also both released on Metropolis Records, but not until 1998. The Dassings still recorded as Mentallo and the Fixer, releasing their next album Burnt Beyond Recognition in 1997, along with two singles: "Centuries" and "False Prophets".

After the departure of Dwayne Dassing from the band in 1999, Gary continued to use the Mentallo and the Fixer name, and released several albums including Algorythum, Love is the Law, Return to Grimpen Ward, and Vengeance is Mine, along with the single "Systematik Ruin" to accompany Alogrythum. Gary Dassing has returned once again after a five-year silence with the newest Mentallo and the Fixer release, Enlightenment through a Chemical Catalyst.

Side Projects include:

Benestrophe (pre Mentallo & the Fixer)
Mainesthai
Shimri (Gary Dassing Solo)
Reign Of Roses (Dwayne Dassing & Scott Berens)