Concert CDs sold on the spot by a radio giant New York Times News Service Clear Channel Communications, the radio broadcasting and concert promotion giant, plans to introduce on Monday a venture that will sell live recordings on compact disc within five minutes of a show's conclusion. The venture, Instant Live, will enable a band's still-sweating fans to leave with a musical souvenir instead of, say, a pricey T-shirt or a glossy program. Although initially modest, involving only small-audience clubs and theaters in the Boston area, the venture could eventually extend beyond radio and concerts into music distribution. And that...