Tremolo unit for string instrument

A tremolo unit applied to a string instrument having a base plate and a plurality of strings, wherein the base plate has a top surface and a back surface and is pivotally supported by a body, wherein a front end of each string is supported by a neck, and a rear end of each string is supported by the top surface of the base plate, wherein the tremolo unit permits the base plate to be pivoted in response to manipulation of a tremolo arm, the tremolo unit comprising:

• a tremolo block, wherein the tremolo block extends vertically from the back surface of the base plate into a space defined in the body and pivots with the base plate, and wherein the tremolo block has hook portion at its distal end;
• a base located at a back portion of the body;
• a pair of engaging sections formed in side sections at a rear portion of the base, wherein each engaging section opens rearward;
• a moving member detachably located at the engaging sections, wherein the moving member is moved between an engaging position, at which the moving member engages with the engaging sections, and a standby position, at which the moving member is separated from the engaging sections;
• a pair of first springs connecting the base with the tremolo block, wherein the first springs urge the tremolo block forward against tension of the strings, and wherein the urging force of the first springs is adjustable;
• and
• a pair of second springs located outward of the first springs, wherein the second springs connect the base with the moving member, wherein the second springs urge the moving member toward the engaging position, and wherein, in a normal state, the second springs hold the moving member at the engaging position,
• wherein, when the tremolo block is stopped or pivoted forward, the moving member is held at the engaging position by the urging force of the second springs, and wherein, when the tremolo block is pivoted rearward, the moving member is moved from the engaging position to the standby position by contact between the moving member and the hook portion.