William Allaudin Mathieu was a disciple of North Indian vocalist Pandit Pran Nath for 25 years. He studied with Bill Russo and Easley Blackwood, and collaborated with Nubian master musician Hamza El Din.

In the 1960s (as Bill Mathieu), he spent several years as an arranger and composer for Stan Kenton and Duke Ellington orchestras. Kenton's album Standards In Silhouette consists entirely of Mathieu's arrangements and revealed the young Mathieu (then 22 years of age) to be an adept manipulator of compositional materials.

He was one of the founders and the musical director for The Second City in Chicago, the first ongoing improvisational theater troupe in the United States, and was later the musical director for The Committee, an improv theater in San Francisco that was an offshoot of The Second City. In the 1970s, he was on the faculties of San Francisco Conservatory of Music and Mills College. In 1969, Allaudin founded the Sufi Choir in San Francisco among followers of Samuel L. Lewis, and he directed the choir until 1982.