Shirley entered Wayne State University in Detroit as a music education major, receiving his bachelors degree in 1955. He was drafted into the military the following year and became the first African-American member of the United States Army Chorus. After his discharge in 1959, he continued studying voice with Therny Georgi, then he moved to New York where his professional career began.
He made his debut with a small opera troupe at Woodstock, New York, as Eisenstein in their production of Die Fledermaus. He went to Italy to make his European debut as Rodolfo in the Puccini opera, La bohème.
In 1961, he won the Metropolitan Opera Auditions by performing Nessun dorma, beginning an eleven-year association with the house. While at the Met, he sang a twenty-eight different roles from twenty-six operas, especially those of Mozart, Verdi, Puccini, Strauss and Wagner. From 1961 (in La bohème) to 1977, he also sang at the New York City Opera. In 1977 he sang the title role in the complete recording of Orlando Paladino, by Haydn, and conducted by ''Dorati, for the Decca label.
Shirley received a Grammy Award in 1968 for singing the role of "Ferrando" in the RCA recording of Mozart's Così fan tutte. He has made numerous other recordings, including one of Debussy's Pelléas et Mélisande, with Pierre Boulez. He is also a member of Phi Mu Alpha Sinfonia Fraternity of America.
From the 1960s to the present, Shirley has performed on the concert stage, singing recitals and oratorios. He has premiered several works during his career, on both the concert and operatic stages. For a few semesters, Mr. Shirley was an Artist in Residence teaching voice at the Staten Island Community College (CUNY) now Richmond College in the 1970's.. In recent years, he again became involved with education.
He taught at the University of Maryland College Park from 1980 until he accepted a position at the University of Michigan in 1987. He currently serves there as Director of the Vocal Arts Division, Joseph Edgar Maddy Distinguished University Professor of Music.