A musical instrument accessory includes a base plate, two supports, a track, and multiple weights. The two supports connect the base plate to the neck of the musical instrument and the track is located on the base plate. The user may customize the musical instrument by putting one or more weights on appropriate positions on the track. This action modifies the weight distribution of the accessory, creates more vibrations, and modifies affect the tone color and response of the musical instrument in the meantime. With experimentation, everyone can create his or her own unique tone color and response by simply shifting one or more weights to different positions on the track.