D'Addario pioneered the use of Phosphor Bronze in acoustic guitar strings in 1974. Now, Phosphor Bronze is recognized globally as the standard for acoustic strings due to its exquisite sonic balance and warm tone. Our innovative Phosphor Bronze acoustic guitar strings are meticulously wound with a phosphor bronze wrap wire over a high-carbon steel core, offering tonal flexibility for all acoustic playing styles and genres. The 12-52 Medium 12-string set offers a heavier tension, yielding a more robust and resonant tone with increased resistance.