a brace type angle - detecting device for musical tone control includes a brace to be fit around a joint portion of a player and an angle - detecting mechanism mounted on the brace for detecting the bending angle of the player &# 39 ; s joint and producing a musical tone control signal in response to the angle of the player &# 39 ; s joint . the angle - detecting mechanism includes first and second elongated members detachably mounted on the brace which are connected to one another so as to be pivotable in a bending direction of the player &# 39 ; s joint . the device includes a fastener for tightly fastening the brace to a body member of the player .