EJ19 Bluegrass acoustic guitar strings from D'Addario, available at DC Music Store! Acoustic Guitar Strings Phosphor Bronze Bluegrass Medium Light. Superb tone that really lasts. Gauges: 12-16-25-35-45-56. D'Addario EJ19 Bluegrass acoustic guitar strings employ a genuine phosphor bronze alloy that retains flexibility as well as brilliant tone for many hours of hard play. Computer-controlled wrapping around a hex core ensures consistency and extends life. Many top guitarists won't play any other brand.