After moving to Austin, Marsh attended concerts by Anthony Braxton and Sam Rivers at Armadillo World Headquarters.
[4] These performances inspired her to form her first professional group, New Visions Ensemble, with Alex Coke, Rock Savage, Booka Michel, and Horatio Rodriguez.
[4] CO2 began as a cooperative organization, similar to the AACM, though Marsh gradually assumed a managerial role and became the group's director.
[4] Marsh went on to perform with Carla Bley, Hamiett Bluiett, Vinny Golia, Dennis González, Billy Hart, Roscoe Mitchell, Steve Swallow, and Kenny Wheeler.
[11] C. Michael Bailey of All About Jazz described Marsh's music as "progressive big band, a kind of marriage between the avant-garde and postmodern classical.