A musical instrument comprising: an actuator (50, 50C, 50D) for vibrating a sound board of the musical instrument comprising: a magnetic path formation section constructed to form a magnetic path space; a bobbin having a voice coil attached thereto in such a manner that the voice coil is disposed within the magnetic path space; a connection member (514, 514A, 514B) connected to said bobbin and constructed to vibrate in response to vibration of said bobbin, said connection member (514, 514A, 514B) having a connection end adapted for connection to the sound board of the musical instrument, said connection member being constructed to be adjustable in length; a support section supporting the magnetic path formation section; the sound board having the connection end connected thereto; a performance operator; and a signal generation section configured to generate a drive signal indicative of an audio waveform corresponding to an operation of said performance operator, the drive signal being supplied to said actuator for driving the voice coil, wherein the actuator further comprises a fixing jig for indicating a reference mounting position, within the magnetic path space, of the voice coil, and the fixing jig is a reference position instructing member for automatically indicating that the relative positions, in the axial direction, of the vibration member and the magnetic circuit member are in the reference mounting position of the voice coil within the magnetic path space, such that the length of the connection member (514, 514A, 514B) is adjustable by adjusting the length of the connection member (514, 514A, 514B) while maintaining the reference mounting position, within the magnetic path space, of the voice coil. an actuator (50, 50C, 50D) for vibrating a sound board of the musical instrument comprising: a magnetic path formation section constructed to form a magnetic path space; a bobbin having a voice coil attached thereto in such a manner that the voice coil is disposed within the magnetic path space; a connection member (514, 514A, 514B) connected to said bobbin and constructed to vibrate in response to vibration of said bobbin, said connection member (514, 514A, 514B) having a connection end adapted for connection to the sound board of the musical instrument, said connection member being constructed to be adjustable in length; a magnetic path formation section constructed to form a magnetic path space; a bobbin having a voice coil attached thereto in such a manner that the voice coil is disposed within the magnetic path space; a connection member (514, 514A, 514B) connected to said bobbin and constructed to vibrate in response to vibration of said bobbin, said connection member (514, 514A, 514B) having a connection end adapted for connection to the sound board of the musical instrument, said connection member being constructed to be adjustable in length; a support section supporting the magnetic path formation section; the sound board having the connection end connected thereto; a performance operator; and a signal generation section configured to generate a drive signal indicative of an audio waveform corresponding to an operation of said performance operator, the drive signal being supplied to said actuator for driving the voice coil, wherein the actuator further comprises a fixing jig for indicating a reference mounting position, within the magnetic path space, of the voice coil, and the fixing jig is a reference position instructing member for automatically indicating that the relative positions, in the axial direction, of the vibration member and the magnetic circuit member are in the reference mounting position of the voice coil within the magnetic path space, such that the length of the connection member (514, 514A, 514B) is adjustable by adjusting the length of the connection member (514, 514A, 514B) while maintaining the reference mounting position, within the magnetic path space, of the voice coil.