More 18++ Martin And Co Acoustic Guitar Strings. Read our guitar string training guide to learn about different important string terminology and best practices when it comes to caring for your strings. 833 martin guitar strings products are offered for sale by suppliers on alibaba.com, of which guitar accounts for 3%, stringed instruments parts & accessories accounts for 1%. In the acoustic fx series, each string is made with a special thin wire core for improved sustain and increased flexibility.