If they hit it big, last night’s Cactus Blossoms show at the Blue Door will be one to remember. The young musicians were tentative and had a couple of false starts before a crowd of about 30 people. But they sounded great, akin to a country and western sock-hop. All night I tried to determine where they fit in the musical landscape, somewhere around the Everly Brothers and Buddy Holly. Which puts them squarely with this Marty Robbins pop-crossover hit.