As regards my previous post on this subject all I can say is mea culpa! I should have said that by placing a weight in the back of the key the downweight is brought to or decreased to 15 grams (thereby increasing upweight). Thankyou Ken. Last week I received, out of the blue, a message from Paul Poletti, a fortepiano maker whom I hadn't heard from in a long time. He used to make instruments in Modesto, Calif. Evidently, he saw a post of mine on another list and decided to contact me. He is presently in Belgium building and restoring fortepianos. So, I put the touchweight question to him and got the following: (this is a bit long) Date: 23 Feb 95 20:04:59 EST From: Paul Poletti <100407.2266@compuserve.com> To: Bill Darst <darst@humanitas.ucsb.edu> Subject: Re: Fortepiano touchweight Hi Bill, Interesting question. It's 1 in the morning, and I have just returned from a typical European "pub crawl" evening, so the synapses are not firing too clearly due to a fresh and rather generous lubrication with Belgian beer (the best in the world, I'm afraid), but I'll try to get a coherent answer off. I don't know if you know it or not, but I am considered to be a sort of expert on Viennese actions among the builders here, mostly because I wrote a rather massive spreadsheet which accurately predicts the functional characteristics of the Prellzungenmechanik by geometric modeling, and then proceeded to plug every original instrument I could my hands on into it to see what came out. Not to blow my own horn , but just to let you know that I've seen a lot of actions. Combined with Michael Latcham's extensive research, which he has fed to me on a regular basis, I think I've either examined personally or been given very good info on well over 100 extant actions. I have *never* seen any lead in any Viennese pre-1830 action that I could even begin to think was original. Nor have I seen any evidence of undercutting, as is often found in harpsichords, beyond a very slight undershaving on the sides only of natural heads, probably more for clearance than balance. Walter does a very curious thing which gives a good hint to the general practice: as you know, the big problem with laying out a keyboard is that C-E is three naturals and five tails (including sharps) and F-B is four naturals and 7 tails, and unfortunately, 3/5 does not equal 4/7. Thus the problem is how to space the sharps relative to naturals in the two different sections. Two solutions have been found in the history of keyboards: (1) divide the back portion of the naturals in the two sections equally, thus your C-D-E will have slightly wider tails than F-G-A-B; (2) keep C & E the same width as F through B and let all the error accumulate in the D tail, which is the normal harpsichord solution. When you do this, you end up with a noticeably wide D tail,which is also heavier. Thus on harpsichords you >often see more undercutting to balance the D key, since the tails at the action >proper are all equal. But Walter keeps his D extra wide all the way back, >even pinning the bridge and cutting the damper rail extra wide around the >note D. Unfortunately, the MINe109 drawing doesn't show this on the >keyboard, though if you look very closely at the spacing of the balance >pins and draw the strings between nut and bridge pin, it jumps right out >at you. This is an "acid test" for a real Walter (or the accuracy of a >copy): just look carefully at the string spacing around every D. Why does >he do it? Obviously, to let the wide key balance with itself without any >undercutting. We have at this moment in our shop three original instruments: a Graf 6 1/2 from about 1825, a Fritz 6 1/2 from the same period, and an early probably Brodmann 6 octave c.1810?. None have either any lead or undercutting. Thus it appears that the only thing that gives balance in the Prellzungenmechanik is the weight of the key-mounted action components themselves. This of course gives an extremely light action, and the keyboard must be totally free and without friction in and of itself. I personally think that slow repetition in these actions is mostly due to either too much friction between the pawl (some call it an "escapement lever", though it is neither an "escapement" nor a "lever" as either are defined by classical mechanics) and the beak leather and/or pawl springs which are too strong. One reads endlessly that the English actions were heavier. I don't measure balance weight, since I just use the same materials as found in the originals and duplicate dimensions and figure balance will take care of itself (which is what they seem to have assumed). However, I do measure functional weight, which is the amount of weight needed to raise the hammer through the moment of escapement, without damper (dampers raised by the pedal or knee lever during the test). The test weight is placed upon the key, which is restrained, and then the key is released, which means there is no kinetic energy of the test weight itself affecting the final results. I have found most Prellzungenmechaniks to have functional weights of 35 to 42 grams in the bass and 21 to 27 grams in the treble, from late 18th-cent 5 octave instruments up to and including late 6 1/2 octave instruments. I recently had the pleasure of seeing a Broadwood 5 1/2 octave from 1792 (positive date) which is in mint condition, unrestored. It had a key dip of 6.5mm consistently and a weight about 5 grams lighter than the Prell actions. But the keys had lead in the front (!) which seemed to be original. Thus even though the balance and functional weight was less, the inertia of the lead made the action *feel* heavier. Another important point is that all, absolutely all, Viennese fortepiano keyboards I have ever seen are made of spruce (or a similar evergreen) and NOT linden (or basswood). A very telling instrument is the Stein 1781 claviorganum (Goteborg museum, currently on loan to Haags Gemeentemuseum), which has two keyboards, one for the piano and one just below it for the organ (which, by the way, slides in and out of the keywell and acts as the sled for raising the piano action above). The organ keyboard is of linden, and the piano keyboard is of spruce. Here again, we see a very subtle refinement in order to make the piano action as fleet and light as possible. My experiments with sitka and bass while I was still in the states indicated that sitka was about 20% lighter than bass. Most modern players are unable to handle real Prellzungenmechaniks because they are so incredibly light. Thus the need for lead or undercutting. I would say copy the action as it is. If it seems too light, live with it for a spell. If it doesn't return well or if repitition is bad, check your Schnabelluft: a healthy 1mm is needed. Also make sure your key is totally frictionless, check for too strong pawl springs, polish the pawl faces and put talc or ground soapstone on the beak leather, and most important, make sure the player is picking his fingers ALL THE WAY UP!!! That's all for the moment. If I think of anything else, I'll send it along later. I also have *extensive* studies in depth of touch, but that is another story. Paul Bill Darst, RPT Music Dept UC Santa Barbara
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