ACOUSTIC GUITAR STRING SET String Sets Acoustic Guitar EJ Series Phosphor Bronze Custom Light (011 - 016 - 024 - 032 - 042 - 052). D'Addario Phosphor Bronze acoustic guitar strings are recognized the world over for their superb, long-lasting tone. Broncede Phosphorus was introduced for string making by D'Addario in 1974 and has become synonymous with warmth, brilliance, and well-balanced acoustic tone. They are D'Addario's most popular acoustic guitar strings.