Marcus is also an accomplished, professional bass guitarist, currently playing in several bands in Los Angeles, including the alternative country artist Olivea Watson. Marcus is also a session musician, and a member of Musician's Local 47. With over thirty years of experience, Marcus is extremely versatile, with strong improvisational skills in all styles ranging from rock, jazz, pop, blues, country, and alternative. Some of the artists Marcus has collaborated with include: Doug Pettibone (Lucinda Williams, Tracy Chapman), Lionel Cole (Mariah Carey, Robert Downey Jr.), Michael Hakes (Edgar Winter), Otis Hayes (Ice-T), Irvin Kramer (Ray Charles), James Montgomery, Will Ray (Hellecasters), XJM Jazz Trio, David McKelvey, Shawn Nourse (Dwight Yoakum), Skip Edwards (Michelle Shocked), Chris Lawrence (The Paladins), Carl Byron (Anne McCue), Percussionist George Martin (Earth, Wind and Fire), drummer Mike Bennett (Chick Chorea), Rebel Soul Band (Winner of Relix Magazine's 2004 Jam Off!), and The Williamstown Cabaret. Marcus recently finished playing bass, and co-producing a record with Dusty Wakeman (Lucinda Williams, Dwight Yoakum, Michelle Shocked) for Olivea Watson, at Mad Dog Studios, in Burbank, California. Marcus is a long time student of jazz master, Todd Johnson.

His extensive theater credits include stints on Broadway in Horton Foote's Young Man From Atlanta, and Measure For Measure at Lincoln Center. Off-Broadway, Marcus has appeared in numerous shows at MTC, The Lambs and WPA. Regionally, he has worked at The Guthrie, Seattle Rep., Yale Rep.,Long Wharf, over 20 productions at The Williamstown Theater Festival, Hartford Stage, New Jersey Shakespeare Festival, The Goodman, and The Eugene O'Neil Playrights Conference.


He is the older brother of Paul Giamatti. Is a graduate of the Yale School of Drama. He has twice played in The Legends and Celebrity Softball Game as part of The Major League All Star Game, in both Pittsburgh (2006) and San Francisco (2007). He was the Captain of his high school varsity swimming team, as a senior, at Hopkins, in New Haven, Connecticut. Received the Carol Dye Award for Excellence in Acting upon his graduation from The Yale School Of Drama. His bass recording work includes sessions with such distinguished musicians as Doug Pettibone, Lucinda Williams, Don Heffington, Bob Dylan, Skip Edwards, Dwight Yoakum, James Brown and drummer Otis Hayes. Marcus' great grandfather, Commodore Alfred Brown, was the first and only man to swim the Panama Canal. This was accomplished with permission from President Teddy Roosevelt in 1913, before the canal was opened to commercial traffic. His grandfather, Abram E. Smith, was the head football coach at Plainfield High School, in New Jersey, from 1943 to 1968. One of his players was Olympic Decathalon Champion Milton Campbell. Marcus received his Actor's Equity card at The Williamstown Theater Festival in 1987. Has performed many of Shakespeare's greatest roles from Henry in "Henry V", to the tittle role in "Macbeth", to Bottom in a Midsummer Night's Dream, and Silvius in "As You Like It'". Brother-in-law of Elizabeth Giamatti. Marcus was a bass student of Jim Stinnett, and The Stinnett School Of Music, an affiliate of The Berklee College of Music, in Boston. Marcus originated the role of Tom Jackson, in the debut Broadway production of Horton Foote's Pulitzer Prize winning and Tony nominated play, The Young Man From Atlanta.