To enjoy a musical performance accompanied by free movement more than before without any hindrance to the musical performance by equipping a body with a battery inside and installing a transmitter connected to a sound volume and tone quality control circuit in the body.

The body 1 is a hollow body which is made of wood, plastic, etc., a control unit 2 which has switches, etc., provided successively on the surface is arranged, and the sound volume and tone quality control circuit is arranged in the control unit 2. The transmitter 3 installed at a proper place in the body 1 is equipped additionally with its driving battery 4 and connected to the sound volume and tone quality control circuit. Then the vibration of steel strings is transduced by the sound volume and tone quality control circuit into electric vibration, which is adjusted to sound volume and tone quality that a player desires and then transmitted by the transmitter 3. The signal transmitted by the transmitter 3 is received by a receiver and supplied to a guitar amplifier.