SET OF STRINGS FOR DOUBLE BASS Helicore '' Orchestral '' nickel wound 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 clear and warm tone. The heart design makes the strings very easy to play under the left hand. These strings have been conceived 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.