A guitar or applicable musical instrument is improved to enhance string energy through integration of side materials and structural spanners to maintain the integrity of the instrument under load of string tension. The invention improves ampliphonic efficiency by protecting the resonating surface of the instrument's soundboard from compression and distortion, stabilizes the harmonic mode of the neck as it rocks in and out of the sound hole area, and decreases loss of string energy. By stabilizing the neck and body structure, a long-term consistency in the neck alignment to the body is preserved. The soundboard efficiency is improved by extending the string load on the structure to the butt end of the instrument, allowing for a greater portion of soundboard area to be de-stressed when under string load.