Largely forgotten outside of music buffs and those who recall their lone 1968 hit, “Summertime Blues,” San Francisco’s Blue Cheer played psychedelic- and blues-twinged hard-rock at deafening volumes: In other words, some argue, they set the stage for heavy metal. Fittingly, this historical band share an 8 p.m. bill at Shank Hall tonight with a beloved but sometimes forgotten band from Milwaukee’s own music history: Plasticland, an act that played vibrant, British-styled psychedelic rock and pop throughout the ’80s.