Fig 7String scaleClick a string or 1–8 to ring itA4 · 440 Hz · 0.42 m · steel 0.95 mm · 78 kgf
The ringing string, its motion drawn about six times largerBridge posts stepping back with each octaveWound bass: copper on steel; the rest plain steel wireA string's pitch is set by its length, its tension and its weight per metre: f = √(T/μ) / 2L. Halve the length and the pitch goes up an octave, so if every string had the same wire and tension, A0 would need 5.6 m against C8's 52 mm. A 2.11 m case allows 1.30 m. The treble follows the doubling rule down to about C3; below that the strings are foreshortened and made heavier instead. The plain steel gets thicker toward the bass, from 0.77 mm at C8 to 1.08 mm at A2, and the lowest notes are wound with copper. A0 is a 1.6 mm steel core wound out to 7.2 mm at 150 kgf; plain, at the same tension, it would need 5.6 m. A1 is wound to 3.4 mm instead of 3.1 m. Every string here pulls between 70 and 150 kgf.