Our New Wave band in 1980-81 had some fans in the physics department of the college we all attended, including the profs. At one Art dept gallery show, one of the physics profs brought a small ring stand with a sheet of latex stretched across it with a small mirror chip on the latex, and placed in front of the PA speaker. He aimed one of the department's laser lights (which was a rarity in those days) at the mirror chip, which was angled to bounce on to a nearby wall. The sound waves provided quite the light show of constantly changing shapes, especially when we ended a song all on the same note, which created an infinity symbol. Low-budget, but relatively high-tech for the times....