Belly Work by Absolute Piano
The structural component of a piano or belly is comprised of the soundboard, bridges, plate (harp), pinblock, and strings. Pianos are strain bearing instruments and differ from stringed instruments with relatively low string tension where sound is produced by bowing or plucking. When a piano string is struck by a hammer, we expect power, sustain, color, and dynamics, and these are achieved by having the right balance of opposing forces. On the one side, we have string tension pressing on the bridges. On the other, we have the soundboard and ribs set in a crowned position, like a disc spring, supporting and resisting the string tension. It is a battle of opposing forces that stresses the soundboard until eventually it needs to be replaced.
The piano's string scale is critically important. The length, diameter, and mass of music wire determines its tension, inharmonicity, acoustical power, and hammer to string contact time. From manipulating the scale, we can adjust the pressure on the bridges and then design a soundboard and rib scale that will not only balance the mass and stiffness of the system, but also support the load longer than was traditionally possible.
While tone is ultimately an aesthetic perception and subjective, our goal is to create an evenness from note to note, with as much acoustical power available as possible, proportionately balanced between loudness and sustain. Many vintage pianos have problems in the original scale and soundboard design that can be corrected. An uneven transition from the bass into the tenor can be smoothed, weakness in the "killer" or sixth octave of the piano can be strengthened, extraneous noise can be reduced, and problems with staying in tune can be mitigated.
At TPR, we assist each client in making the best choices for their piano depending on the piano's condition and the desired outcome. We purchase lumber directly from the sawyer to manufacture our own soundboard panels, giving us better control over our final product. We also offer rebuilding supplies including soundboard panels to some of the best rebuilders in the country, creating a beneficial feedback loop with our colleagues in the field.
Our belly services include:
1. Disassembly & design analysis (Scale, rib, board & bearing data)
2. T&G Sitka Spruce panel (Specify CC, RC or RC&S)
i. Thickness tapered up to 9mm, diaphragmatic or full
ii. Scale design analyzed to match hammer selection and soundboard design
iii. Grain density, angle, and VG
iv. Decal included
v. Rubbed nitrocellose lacquer finish
vi. All buttons, acoustical dowels, moldings and any other existing details replaced
3. Ribs (Specify sugarpine, spruce or laminated)
i. Redimensioned to accommodate scale/load
ii. Radiused to design spec
iii. Tapered traditionally or in "3rds"
4. Bridgecaps (specify quartered maple or laminated)
i. Rescaled as is practical w/o new root
ii. Downbearing reset to coincide with soundboard crown and design
iii. Brigepin pattern replicated and refined as necessary
iv. Notched, drilled, and pinned
v. Surfaces varnished and graphited
vi. Copper or nickel plated bridge pins
vii. Dowelled and buttoned
5. Plate (Harp)
i. Completely prepped, filled, epoxy primed and gilded
ii. Hand lettered with enamel
iii. Plate decals (scale, serial #, ebonized etc.) applied
iv. Finished with clear coat
v. Washers installed under all nosebolts and perimeter bolts to protect finish
vi. Capos resurfaced, work-hardened, and lubricated
vii. Optional modification of duplexes
viii. All hardware plated (rear duplexes, aliquots, webbing screws etc.)
ix. Felt muted string terminations
x. Rear duplexes or aliquots tuned
xi. New agraffes installed
xii. Original agraffes polished if replacements are unavailable
xiii. Tulip nuts, perimeter lag bolts, and pinblock screws cleaned, plated and/or polished
xiv. WNG adjustable perimeter bolts installed
6. Pinblock
i. Delignit capped multilam double-drilled to 125 PSI (Delignit, multilam, Hexagrip also available)
ii. Full-fit, dowelled, and epoxy formed to flange
iii. Varnished
iv. Proper string heights and plate height/level verified appropriate to design
7. Strings
i. New nickel-plated Diamond tuning pins
ii. German Roslau steel wire
iii. Custom scaled bass strings
iv. Plain wire rescaled as necessary
v. Stringing braid run through non-speaking string segments where appropriate
8. Optional modifications
i. Radial rib design
ii. Unhinged or floating bass bridge (under 6')
iii. Impedance devices (bass cut-off and treble fish)
iv. Bass redesigned to eliminate cantilevered bridge
v. Transitional bridge
vi. New treble bridge
vii. Vertical hitches
viii. Mass loading of bridge to fine tune the soundboard impedance
ix. Belly and add additional framing members mass load as needed
Jude Reveley, RPT