Clarence Fountain, founder of the Blind Boys of Alabama, has one ambition left after more than half a century of singing gospel. "I want to sell a million records," he says flatly. He knows he could have done that long ago by converting to secular music, as his peers Sam Cooke and Little Richard did. But Fountain was never tempted. "I've stayed on the path," he says. Few singers of Fountain's age possess his assured perseverance; few groups formed in the Depression era are still performing, and none - Blind Boys excepted - can look back on this past decade as its most successful.

The Blind Boys of Alabama have been pilgrims on the Gospel Highway for nearly 60 years, albeit with a few personnel changes along the way. They are to gospel music what the Rolling Stones are to rock, what the Berlin Philharmonic is to classical music. Fountain started singing in 1937 with his classmates at Alabama's Talledega Institute for the Deaf and Blind, and made his recording debut with them (as the Blind Boys) 11 years later. They hit the jackpot in 1988 when they starred with actor Morgan Freeman in the Obie-winning Broadway musical, The Gospel at Colonus. In the intervening years, they toured relentlessly, showcasing their I-dare-you-not-to-get-up-and-move enthusiasm and legendary Southern gospel style, which prominently features Fountain's gravelly baritone.

The Blind Boys' phenomenal popularity stems from intense, invigorating vocals, seemingly effortless harmonies, and a gritty, revival-style spirituality that would move even a confirmed pagan. Their repertoire gets the full gospel treatment, and they turn even Pete Seeger's folk standard, "If I Had a Hammer," into a scorching pledge of redemption.

Gospel acts have only been at Cambridge over the last few years. All have been excellent and this year should be no exception.