William P. Foster received his bachelor's degree from the University of Kansas (Lawrence, Kansas), in 1941. He went on to receive a master's degree from Wayne State University in 1950, a Doctor of Education with a major in music from Teachers College, Columbia University, in 1955, and the Honorary Doctor of Humane Letters from Florida A & M University (FAMU) in 1998.

Foster served as the band conductor for Florida A & M University, where he created a broad range of innovations in the field of marching band Pageantry. The FAMU Marching 100 is known internationally. Dr. Foster created over 200 halftime pageants for the band, the band appeared on the television programs "60 Minutes" and "20/20" and in three films, three commercials, numerous magazine and newspaper articles, and 34 nationally televised performances seen by over 5 billion viewers. The Marching 100 was also the only American marching band featured in the French Bicentennial Parade. The Marching 100 has been the centerpiece of many public events including the 15th and 25th anniversaries of Walt Disney World.

When not conducting the Marching 100, Foster authored Band Pageantry, the preeminent textbook on marching band pageants, as well as 18 articles for professional journals and more than 20 musical and marching band clinics all over the country. He also served as a guest lecturer at universities throughout the country and as guest conductor for the US Air Force Band, US Army Band, Interlochen Arts Academy Band, McDonald's All-American High School Band and others. Foster composed several scores of music including "March Brilliante," "National Honors March," "March Continentale," and "Centennial Celebration."

Foster retired from conducting the Marching 100 and went on to serve on the Arts Council under President Bill Clinton and started the William P. Foster Foundation, which strives to help less fortunate members of the marching 100 achieve their educational and life goals. Dr. Foster was a member of the G. Leblanc Corporation, John Philip Sousa Foundation, Tallahassee's Symphony Orchestra, International Music Festival, The Marching Musician, American Band Masters Association, College Band Director National Association (CBDNA), National Bandmasters Association (NBA), Florida Music Educators Association (FMEA), National Association for Music Education (MENC), Phi Mu Alpha Sinfonia, Kappa Kappa Psi National Band Fraternity, Phi Beta Mu National Bandmasters Fraternity, Sigma Pi Phi Fraternity, Alpha Phi Alpha Fraternity, John Philip Sousa Foundation, and The Afro-American Hall of Fame. He had a wife, Mary Ann Foster, and two sons, William P. Foster and Anthony Frederick Foster. William P. Foster died at the age of 91 in August 2010.