Originally David Richard Solberg, he was born the son of a Lutheran minister. His father, Dr. Richard Solberg, was a senior representative for Lutheran World Relief during the reconstruction of Germany after World War II, and the family moved frequently while Soul was growing up.

Soul first gained attention as the level-headed Joshua Bolt on the television program Here Come the Brides, but became famous for Starsky and Hutch. He has also made guest appearances on shows such as I Dream of Jeannie, Cannon, Gunsmoke, World War III (miniseries), Star Trek, and The Streets of San Francisco. His best known film appearance was opposite Clint Eastwood in Magnum Force.

After a successful singing career, including #1 hits such as "Don't Give Up On Us" and "Silver Lady", Soul moved to the United Kingdom, and notably participated in the successful 1997 election campaign of Martin Bell. In September 2004 he became a British citizen, but it is not clear if he relinquished his U.S. citizenship. Around Easter 2005, he had a vacation to Cuba, illegal for US citizens in most cases. He has been married four times, and had a long-term relationship with Alexa Hamilton. He has six children: five sons and one daughter. His brother Daniel Solberg is pastor of St. Paulus Lutheran Church in San Francisco, California.

On July 12, 2004, he took over playing the role of Jerry Springer in Jerry Springer - The Opera at the Cambridge Theatre in London. He is currently back in the West End playing Mack in a new production of Jerry Herman's musical Mack and Mabel at the Criterion Theatre alongside Janie Dee. The production is directed by John Doyle.