Pirastro Obligato Viola StringsObligato are modern synthetic core strings with a warm, brilliant and full sound. They have big and powerful tone volume and excellent response. Features: Obligato strings have a core made from a modern synthetic multifilament fibre. Obligato strings sound warm and full, yet have a brilliant, rich overtone spectrum and focused tone. Excellent playability and response throughout the entire dynamic range. Great tone volume. Excellent tuning stability.