LOOSE STRING FOR DOUBLE BASS Helicore Orquestral '', Sol (G), H 611 3/4 medium tension. Helicore Orchestral Strings for Double Bass are made with a core made up of several braided steel threads, which produces a warm and clear tone. The heart design makes the strings very easy to play under the left hand. These strings are intended for use with the bow, making them ideal for symphonic use. Helicore orchestral strings are also ideal for use on pizzicatos where they offer us a very warm sound and with less sustain.