ACOUSTIC GUITAR STRING SET String Sets Acoustic Guitar 12 strings, Phosphor Bronze Light (010/010 - 014/014 - 023/008 - 030/012 - 038/018 - 048/027). D'Addario Phosphor Bronze acoustic guitar strings are recognized the world over for their superb, long-lasting tone. Phosphor Bronze 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.