Chuck Berry at Summerfest in Milwaukee - 1971 Sonic provided the backline for the Main Stage at Summerfest in 1971. Two Sonic 200 Series enclosures are in view in this photo. Please click on the image to advance to the next photo. 2001 | 1999 | 1997 | 1996 | 1995 | 1994 | 1993 1991 | 1989 | 1988 | 1987 | 1985 | 1984 | 1982 1970s | 1960s | Magazine Ads | Photos |