Brian Speiser was They Might Be Giants' front of house soundman through 2008. He started doing sound engineering at live shows in 2000 at age 22, two years into his career. He was the one responsible for the digital recordings of shows offered from They Might Be Downloads from 2004 to 2007 (along with Dan Miller), and is also given recording credits for The Spine Hits The Road, Almanac, and the live tracks from Venue Songs. On the latter, he is credited with engineering and mixing the album. He is also credited with mixing the live rendition of "She's Actual Size" for 2002's Dial-A-Song compilation.
In addition, he has given his approval to the animated video for "Bastard Wants To Hit Me" as an expert cinéaste and can be found namechecked on TMBG's family podcast as a five-year-old who writes to the Johns with a question.
Apart from his work with TMBG, he did sound for People Are Wrong! and produced two albums by the band Common Rotation: The Big Fear and Isalie, on which John Linnell and all three Dans are guest musicians.