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CLAVIERS BAROQUES -- Library of Stringing Schedules

C. F. Sönderberg, Kjöbenhavn (Copenhagen) double-strung square fortepiano (undated, ca 1820), marked No. 14, as restrung by Claviers Baroques 2002

This lovely square forte-piano had had the bad fortune to have been "rebuilt" during the 1960's by a piano tech/'restorer' who restrung it in modern piano wire (tension two to three times that of the original wire), to the great detriment of the case. When we first picked up this instrument it was standing on three legs as the tension of the wire tried to fold the it in half diagonally. Our first action was to slack off the strings and the case immediately began to relax. We continued to reduce the tension slowly over several months to allow the case to regain its original shape as much as possible without stressing the joints. Finally we felt we could safely remove the strings altogether. There was some damage we could not repair and some parts had been removed -- there are the marks of a moderator of some sort, probably a sordine, that apparently would not would not fit with the "improved" felted hammers, the two knee levers had been removed at some time and replaced with a clumsy foot-pedal, there were several other modifications and repairs that had been done over the instruments 200 year history. The case was sound, however, and the action parts were still mostly intact. The owners' request was that the piano be made playable, and that its history be respected, but a complete "museum quality" restoration was not wanted. We therefore approached this as an exercise in extreme maintenance.

We are most grateful to the generosity of the innumerable experts, friends, colleagues and lovers of old pianos whom we consulted during the course of this repair for sharing their expertise and experience with us. The following stringing schedule is based largely on the work of our Australian colleague Carey Beebe, who restored a similar fortepiano, a Rädecker & Lunau Square c1830 owned by Hong Kong University Music Department.

String number*

Notes (Helmholtz)



Actual length*
Pairs 73 to 75 (3 pairs) f'''' to g'''' soft iron .014" / 0.36mm  
Pairs 67 to 72 (6 pairs) b''' to e'''' soft iron .016" / 0.40mm  
Pairs 61 to 66 (6 pairs) f''' to a#''' soft iron .018" / 0.44mm  
Pairs 49 to 60 (12 pairs) f'' to e''' soft iron .020" / 0.52mm  
Pairs 31 to 48 (18 pairs) b to e'' soft iron .023" /  
Pairs 23 to 30 (8 pairs) d# to a# soft iron .026" /  
Pairs 19 to 22 (4 pairs) B to d soft iron .030" /  
Pairs 17 and 18 (2 pairs) A and A# yellow brass .030" /  
Pairs 14 to 16 (3 pairs) F# to G# yellow brass .033" /  
Pairs 11 to 13 (3 pairs) D# to F red brass .033" /  
Pair 10 (1 pair, wound) D yellow brass/copper .032" +.010@1.5mm  
Pair 9 (1 pair, wound) C# yellow brass/copper .032" +.012@1.5mm  
Pair 8 (1 pair, wound) C yellow brass/copper .032" +.013@1.2mm  
Pair 7 (1 pair, wound) BB yellow brass/copper .032" +.014@1.2mm  
Pair 6 (1 pair, wound) AA# yellow brass/copper .032" +.016@1.5mm  
Pair 5 (1 pair, wound) AA yellow brass/copper .032" +.016@1.2mm  
Pair 4 (1 pair, wound) GG# yellow brass/copper .032" +.018@1.2mm  
Pair 3 (1 pair, wound) GG yellow brass/copper .036" +.018@1.2mm  
Pair 2 (1 pair, wound) FF# yellow brass/copper .036" +.020@1.2mm  
Pair 1 (1 pair, wound) FF yellow brass/copper .036" +.022@1.2mm  

*Strings, keys and jacks are traditionally counted from the left (lowest note), although stringing schedules traditionally list wire from the highest note to the lowest, probably because most builders string the treble first. It is confusing, I know; sorry.

The "actual length" is for our reference, although you are welcome to use it, if it is of any help to you. It is the length of the pre-looped replacement string we make, which is long enough to replace the longest string of that diameter on the instrument with enough extra for a generous coil. It is not the sounding length.







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