Phosphor Bronze Wound Singles provide a warm, bright, and well balanced acoustic tone. Available in various gauges.Pioneered in 1974 and still revered today, Phosphor Bronze has become synonymous with warm, well-balanced acoustic tone. D'Addario Phosphor Bronze strings are precision wound with corrosion-resistant phosphor bronze onto a carefully drawn, hexagonally shaped, high carbon steel core. The result is long-lasting, bright sounding tone with excellent intonation.