The bracing of the top, respectively positioning and shaping, is one of the main factors influencing the sound.
Classical Guitar: Top BracingAcoustic Guitar: X-Bracing and TentallonesAcoustic Guitar: Bevel and LiningAcoustic Guitar: Chiselling the Back StrutsAcoustic Guitar: Shaping the Back StrutsAcoustic Guitar: Working the Top Bracing