She appeared frequently in performances with Opera Ebony and the Boys Choir of Harlem in addition to touring widely as a recitalist and concert soprano.
[4] After studying singing in her native city with J. Oscar Miller, she earned a bachelor's degree in vocal performance from Central State University in 1965.
[9][1] That same year she was the soprano soloist in Beethoven's Egmont with the Cosmopolitan Young Peoples Symphony Orchestra under Chilean conductor Juan Pablo Izquierdo at Philharmonic Hall.
[7] That same year she was the featured soloist in the inaugural concert of the St. Louis Symphony Youth Orchestra with conductor Leonard Slatkin, performing works by Mozart, Puccini, and Gershwin.
[20] In 1973 Mathis and William Warfield were the featured performers at the National Association of Negro Musicians convention in Atlanta with conductor Everett Lee.
"[24] In 1976 Mathis created the role of Celestina in the world premiere of Roger Ames's opera Amistad at the John F. Kennedy Center for the Performing Arts.
[30] The following December she performed the role Siebel in Gounod's Faust with that company at Aaron Davis Hall of the City College of New York.