Johnston's compositional style is eclectic. He uses serial processes, folk song idioms (string quartets 4, 5, and 10), repetitive processes, traditional forms like fugue and variations, and intuitive processes. His main goal "has been to reestablish just intonation as a viable part of our musical tradition". According to Mark Swed, "ultimately, what Johnston has done, more than any other composer with roots in the great American musical experiments of the '50s and '60s, is to translate those radical approaches to the nature of music into a music that is immediately apprehensible".