LOOSE ROPE FOR VIOLIN Zyex DZ311 steel, Mi (E), 4/4 medium tension. Synthetic string core Zyex compound produces an extremely warm and rich sound. Zyex is a new generation synthetic material, developed to create incredibly stable ropes under drastic weather conditions. Zyex strings adapt to the instrument very quickly, in a matter of hours. Zyex strings have a warmer sound than most synthetic strings, they also have an excellent projection which makes them exceptional, both for use in solos and for symphonic use.