Mantia has partnered with musician Melissa Reese on several projects, a composing team dubbed "Brain and Melissa". In 2010, along with Buckethead, they released the multi-CD sets "Kind Regards" and "Best Regards". Brain and Melissa composed part of the soundtrack to the video game Infamous 2, for which they were nominated for "Outstanding Achievement in Original Composition" by the Academy of Interactive Arts and Sciences awards. Other video games the duo worked on include, "PlayStation Home", "ModNation Racers", "Twisted Metal", ' and ' (received the nomination "Original Dramatic Score, Franchise" at the 2014 NAVGTR Awards, shared with Marc Canham and Nathan Johnson). They also scored the films "Detention" and "Power/Rangers". They have worked with music video director Joseph Kahn on several television commercials, including NASCAR, SEAT, and Qoros. In addition, they scored a commercial for Johnnie Walker Blue which featured a computer-generated Bruce Lee. They also worked on several remixes of songs off of "Chinese Democracy" for a planned remix album.