Piano stringing-scale design
Albert E. Sanderson · The Journal of the Acoustical Society of America · 1987
Stringing-scale design in pianos comprises the specification of the speaking length of each note, the number of strings per note (unichord, bichord, or trichord), the diameters for all plain-wire notes, and the diameter of the core and diameter and length of the copper winding for all loaded strings. These factors control the inharmonicity and tension of each string, and control of both is essential for excellent volume, tone quality, and balance of sound from baas to treble in a fine grand piano. While there is no accounting for taste, there is general agreement on which pianos sound best. Design rules have been derived based on these pianos, as well as on a large number of poor pianos, that reliably predict what ranges of the above design parameters will “sound good.” In general, the larger the piano, the more tension and the less inharmonicity it must have for excellent tone quality. Inharmonicity must also be carefully controlled to achieve perfect tunability. This is a rare quality that allows an instrument to be tuned so well that every musical interval (when played in ascending sequential semitones) increases smoothly and evenly in beat rate.