Agent Orange is one of the most influential American rock bands most people have never heard. Started in 1979, the Orange County, California, trio made an underground name combining the vibrato reverb of ’60s surf music with the speedy aggressions of American hardcore. “Living in Darkness,” the group’s seminal debut EP released in 1981 on Posh Boy Records, is widely regarded as a masterpiece in obsessive, music-nerd circles for good reason: It stands the test of time. Listening to it today is just as immediate and hard-hitting as it was the day it came out — melodic, vital and timeless. Mike Palm, the band’s principal songwriter, vocalist and guitarist, brings his latest incarnation of the group to Bandito’s Burrito Lounge for a show Thursday, Aug. 27. Richmond bands Chrome Daddy Disco and Dismal Swamp Lords open. Doors at 9 p.m. Free.