LOOSE STRING FOR CLASSIC GUITAR Single strings Pro Arte Composite Series E-6 Wound Composite Strong Tension. Pro-Arte Composite strings are constructed with a unique multi-filament core that improves string life and consistency. Like all Pro-Arte strings, the sets are classified by a highly sophisticated computer controlled laser machine that performs diameter / tension measurements and quality control to ensure perfect intonation. Composite games develop additional projection. The third string provides more tonal flexibility and a balanced volume transition between bass and treble. The slightly polished strings reduce finger noise noticeably, making them ideal for recording.