LOOSE STRING FOR DOUBLE BASS D'Addario Prelude J613 1 / 4Medium Bass String (A). Braided steel core and stainless steel wound. Prelude Double Bass Strings have a braided steel multi-core that produces warm sound quality with good bow response. The special core design and tension reduction make these strings easy to play, especially for younger developing performers. Ideal for use in educational settings, the Prelude Bass Strings maintain a clear, warm sound that blends well into the ensemble.