Stringing: Clavichord & other early keyboards (16th / 17th / 18th century)
Clavichord & other early keyboards (16th - 18th c.)
Clavichord by Andrew Hartig (2013/2020) after the anonymous clavichord (c. 1620) in the Mirrey collection, Edinburgh.
I have found twined strings to work well in the bass range of clavichords and other keyboards in three circumstances:
when the bass is extremely foreshortened so much that plain strings don't sound well, in particular on the short-octave notes C, D and E
as a replacement for overwound strings, or
as a replacement for red brass strings.
In all three instances, the twined strings provide a more flexible string where the sound of a plain monofilament string is unsatisfactory. Since twined strings have more elasticity than plain wire strings of an equivalent mass, they have more higher harmonics, providing both good fundamental and greater clarity in tone. In addition, the greater elasticity translates to greater stretch, meaning that fine-tuning of the bass strings becomes much easier than with heavier monofilament wires where a tiny turn of the tuning pin cause a large change in pitch.
Literary evidence of the use of twined strings in keyboard instruments
Though ample evidence of the use of twined strings for plucked, fretted instruments from the mid-16th century exists, the earliest (and only?) written evidence I know of so far for the use of twined strings in the bass range of the clavichord comes from the 17th century from Mersenne's Harmonie Universelle (1636). First, in Part II, Livre II, Proposition XV, p. 98-99, Mersenne explains the use of twined strings on third and fourth courses of the cittern:
"J'adiousteray seulement ce qu'il y peut avoir de particulier apres avoir donné la figure dans laquelle la plus grosse chorde du 3, & du 4. rang est tortillée, & faites d’vne chorde redoublée & pliée en deux, afin de faire des sons plus remplis, & plus nourris."
("I will only add what can be special after having given the figure in which the largest string of the 3rd and 4th course is twisted, and made of a doubled string, folded in two, in order to make sounds fuller and more entertaining.")
Some 15 pages later (Part II, Livre III, Proposition IV, p. 114), Mersenne references twined strings when describing the bridges of the clavichord in his illustration:
"Quant au cheualets, le premier porte six rangs de chordes, c’est à dire 12. Le second en a 9. rangs ou 18. dont les 8. premiers sont redoublées & retorces, de sorte qu’il y a 20 chordes en double."
("As for the bridges, the first [one] carries six courses of strings, that is to say 12 [strings]. The second has 9 rows or 18 [strings]. of which the first 8 [strings] are doubled & twisted, so that there are 20 pairs of strings.") [Note 1]
Possible physical evidence of the use of twined strings in keyboard instruments
Keyboard maker Owen Daly kindly called to my attention two instances of early keyboards that were discovered to have some evidence of twined strings.
The first of these is the 1581 Hans Rucker's virginals at the Metropolitan Museum in New York. When it was acquired by the museum in 1929, two of the bass strings were of the twisted type. This was captured in a photograph of the rose taken by the museum, as can be seen clearly here on the Met's web site. (The photo is upside down, so the bass strings appear on the top of the photo.) Sadly, at some point during its restoration, the strings were discarded. Associate conservator Stewart Pollens wrote extensively about these strings [Note 2], including exploration of the probability of their originality and analysis of the strings and possible reconstruction based on the photographic evidence and mathematical calculation. In Pollens' words, "The virtual absence of examples or mention of this type of string precludes its adoption from other sources and suggests that twisted bass or short-octave strings may have been originally fitted to the 1581 virginal." (90, 92).
The second instance is a harpsichord from 1699 by Claude Labreche, built in Capentras near Avignon, in which the lowest string is currently fitted with a twined iron or steel string. In Daly's words, "My own guess is that this iron twined bass string was a later replacement trying to copy what they may have found surviving, most likely in brass, [since] sticking iron piano wire in harpsichords where it doesn’t belong was a wide-spread 19th- and even early-20th century bit of abuse." [Note 3]
In addition to these, Pollens' article also notes two other instances of twined strings found in early keyboard instruments:
"a late-eighteenth- or early-nineteenth-century Spanish clavichord (now in the Marlow Sigal collection)" and
"recently fitted bass strings in a short-cased fortepiano by Carl Lemme of Braunschweig (in the collection of Mrs. Seward Johnson; restored in Berlin in the 1970s by Horst Rase, who fabricated strings that presumably replicated the originals)." (90)
More about these last two instruments, I do not know at present.
String tension and twined strings
Because the constituent strands are being pulled at an angle to the direction of force on the string, a twined string will break under less tension than a plain wire of equivalent mass. While this poses no problem for most strings, one does need to be advised that a twined string will not work under extremely high tension or in a range in which a monofilament string works just fine. If you desire to try twined strings on your keyboard instrument, I am happy to work with you and advise you on whether their use would be appropriate for your intended application. In general though, twined strings work seamlessly for strings of the lowest range of historic clavichords, virginals, spinets, and harpsichords.
Much appreciation to Peter Bavington for recording this reference in his article "'Twined' Strings for Clavichords," http://www.peter-bavington.co.uk/twined.htm
Pollens, Stewart: "Flemish Harpsichords and Virginals in The Metropolitan Museum of Art: An Analysis of Early Alterations and Restorations," Metropolitan Museum Journal, v. 32 (1997). The full article can be downloaded and read here. The section about the twined strings begins on p. 88. Calculations of the diameters, twist rate, and breaking pitches for the twined strings can be found in the Appendix, Part II, starting on p. 106.
Private correspondence, 27 March, 2023.