Marching band string instruments and wearable string instruments are described that include a stiff waist band to prevent excessive side to side movement during use, while providing easy doff and don of the string instrument. String instruments also are provided with adjustable chest braces to allow accommodation for different player sizes and for minimization of back strain when playing the electric string instrument for extended time periods. Electric string instruments optionally have soft material interposed between bridge feet and a string instrument body, to allow a more resonant sound detection from a pickup located between the bridge feet and the body. Other advances include generation of a stereo signal from bridge vibrations, and electronic processing of sound that enhances the electric string instrument playing and learning experience.