Ending weeks of speculation, Billy Joel has announced he will perform six concerts in the Soviet Union this summer. "I intend to do a lot of walking around and hanging out," he told a news conference in New York. Joel said he would play three concerts in Moscow on July 26, 27 and 29 and three in Leningrad on Aug. 2, 3 and 5, all in indoor arenas. "I'm not a politician," Joel said. "I am going there as a musician. I want to get more communications going" between Americans and Soviets. He said he hoped to be able to play with Soviet rock musicians. "We don't know a lot about their rock bands, but I'd like to find out," he said.