High-grade, straight-grained, quarter-sawn spruce is used for its resonant qualities and for its high strength-to-mass ratio. The soundboard is solid and not laminated, creating the best resonance and projection of sound In 1936, Steinway patented the diaphragmatic soundboard, designed to be thicker in the middle and gently tapered to the edges. The Boston soundboard has tapered thickness from bass to treble. A thinner soundboard in the bass area vibrates more freely. So you get a bigger, richer, fuller tone.