Anagraffe is a metal device originally designed by Sebastian Erard in 1807, to keep the strings equally spaced and held firmly in position so to counter the blow of the hammer strike. The agraffe string retaining concept has been adapted and substantially modified to retain strings in a number of different configurations since the original Erard design. John Broadwood & Son applied a bridge agraffe to their pianos during the early part of the 20th century. Although the principle was similar to the Stuart design, the application differed in that the knife edges were placed in the opposite configuration. The Broadwood application used a standard load bearing soundboard design concept. There are no records of the sound of this particular Broadwood design. In the Stuart piano the bridge agraffe has been adapted to form a three point coupling device through which the strings pass.
Wayne Stuart writes,
My bridge agraffe application is not an adaptation to resolve the limitations of the pinned bridge but rather, to wilfully enhance the tonal and dynamic parameters of the acoustic piano. I make no claim to uphold the traditional piano as an aesthetic norm but rather, to offer a solution to how the instrument’s sound might be enhanced and further developed along new trajectories. I am of the opinion that earlier attempts to utilise vertical agraffe string coupling devices fell foul of prevailing and often entrenched sound fashions. Combinations were often technically inadequate and/or limited mostly posing as solutions to split pinned bridges. 148
At the heart of the Stuart piano’s sound production is a device designed by Wayne Stuart that couples149 the piano strings to the bridge and soundboard in a different way to all other pianos. The device is the bridge agraffe.
Vertical string coupling is at the core of the Stuart & Sons design concept. A special device (agraffe) is used to couple the strings to the bridge and soundboard structure. The agraffe defines the string’s speaking length (frequency) and contains the reaction forces produced by bending the strings as they pass through it. This negates the need for string down bearing that is required in the traditional pinned bridge system. The soundboard can thus be designed on a speaker cone principle and not as a load bearing structure as is the case in the standard [modern] piano. This scientifically designed device encourages the strings to vibrate in a more controlled manner improving the dynamic range, increasing sustain and significantly improving tonal clarity sympathetic to the entire piano repertoire. 150
Piano strings of all pianos are coupled to the bridge to enable the transmission of the relatively quiet tonal vibrations of the strings into the soundboard, which by the subsequent movement of its greater surface area, the soundboard amplifies and projects the sound.The Stuart bridge agraffe transfers the string vibration modes to the bridge and soundboard without a down-bearing force.
148Wayne Stuart, email interview with author,4th April, 2012.
1149 Term for attach, ‘couple’.
150 Wayne Stuart, email interview with author,4th April, 2012.
