Born in western Brazil of missionary parents, Karlos Moser received his musical training in Denver, Colorado under Antonia Brico.
Moser trained with impresario Boris Goldovsky in conducting, directing and producing opera.
At UW–Madison as Professor of Music, Artistic Director and Conductor of The Opera, he produced and conducted over 70 operas from 1960 until his retirement in 1998, including the American premieres of Haydn's L'isola disabitata and Piccinni's La buona figliuola.
In addition to his work in the UW–Madison School of Music, Moser was founding conductor of the Fox Valley Symphony, director of the Wisconsin Youth Symphony Orchestra, and co-founder of the Original Hyperion Oriental Fox Trot Orchestra.
In 2000 he produced and conducted the original opera Esperanza, inspired by and adapted from the screenplay for the 1954 film about the labor movement, Salt of the Earth.