1a.5 Steel String Limitations

Pianos have to be designed around these limitations and most of the issues in traditional designs stem from music wire limitations. The 7 trichord bass string groupings of the model D Steinway is a classic example of music wire limitations.⁵¹²

The problem with thin wound strings is that they are unstable and often sound rather poor. In this region[tenor strings]the very thin core and covering combinations are also weak in sound and Steinway uses three instead of two. Wound strings are harmonically incompatible , ….. two are bearable, but three are often noisy and unbearable… a very poor compromise.⁵¹³

1a.7 C2 Scaling

The contrasting dimensions of the Paullelo and Roslau piano wires of C2 65.406 Hz are illustrated in table 1a.3 above. The diameter of the Paulello/Stuart core wire is .125mm thicker than the Steinway/Roslau wire, the Paulello/Stuart cover wire is .47mm thicker and of Stainless Steel, whereas the Steinway/Roslau strings are wrapped in copper. Stainless steel is 1.9g per cubic cm lighter than copper in specific gravity⁵¹⁴ . The tensile strength of the Paulello/Stuart wire is 481 N/mm² higher than the Steinway/Roslau. The Paulello/Stuart strings are 235mm longer, and are set at 65.3kg higher tension. The higher tension imposed on the Paulello string is possible because its mass and length are greater, and Paulello’s tensile strength is significantly greater than the Roslau, illustrated by the breaking point figures. The yield or capacity of the Paulello/Stuart. wire is 46% higher than Steinway/Roslau. The composite of materials used, and the proportion of the amount of tension to the breaking point of the string are a matter of tone and the taste/choice of the piano maker.

The Stuart strings are significantly longer, a factor which is known to reduce inharmonicity of wound strings⁵¹⁵ . A reduction of inharmonicity means reduced prominence of the inharmonic frequencies of the string, resulting in a more pure sonorous sound. A wire with a higher capacity of yield produces a more satisfactory sound.⁵¹⁶

1a.8 C3 Scaling

The scaling of the strings for C3 130.81Hz, of the Steinway and Stuart, present a different scenario to C2. The strings for C3, are set in trichords of steel music wire, Stuart using Paulello ‘M’ wire, and Steinway using Roslau wire, both of similar thickness 1.125mm. The Steinway strings are longer by 41.5mm, and the composite materials of the steel wires are different, with differing drawing methods producing contrasting yield and breaking points. The tensile strength and stress % of the yield point is greater in the Paulello string by 140 Newtons per square millimetre (N/mm2). The different rates of tension illustrated in table 1a.4 in the C3 appendix, are part of the equation due to differing string lengths and string material stiffness. The contrasting ‘hardness-stiffness’ of the music wire is illustrated by the contrasting breaking point, the higher the breaking point potential, and the harder or stiffer the wire.

…..the string , considered in its length, diameter, tension and point of agitation, is the most important factor in the production of tone.⁵¹⁷

The combinations of string length and string wire ‘hardness’ affect the amount of movement generated in the bridge and soundboard by the string vibration. This influences tonal colour. The piano maker therefore adjusts combinations of length and hardness in the string to achieve the required tonal colour.

Tonal balance and sustain are the main differences between Röslau wire and Paulello wire.⁵¹⁸

⁵¹²Wayne Stuart email interview with author, 23rd November, 2012.
⁵¹³ Wayne Stuart email interview with author, 5th March,2014.
⁵¹⁴http://www.csgnetwork.com/specificgravmettable.html (accessed July 2014)
^{515     4}Fletcher &. Rossing, 388.
^{516     5}Fletcher &. Rossing, 362.
^{517     8} Wolfenden,15.
⁵¹⁸ Stephen Paulello email interview with author, 14th April, 2014.