Santana, the Doobie Brothers, Bonnie Raitt and James Taylor will join their Soviet counterparts in a July 4 rock concert in Moscow produced by Bill Graham, according to organizers of the American Soviet Peace March. The six-hour show, to take place in the 25,000-seat Dynamo Stadium, will cost $600,000--most of which will be paid by Apple Computer founder and US Festival sponsor Steve Wozniak. "They've never had anything even closely resembling this in Russia," said Graham, who has made two trips to Moscow in the past month to help organize the event. "It's outdoors, a co-Soviet-U.S. concert. It's free and it's in Moscow--on the Fourth of July."