Early in January, a friend asked on the hspchd list about how to deal with slipping loops of brass strings. I’m giving here a cross-section of the most valuable bits of the following discussion, with an emphasis on my own experience.
I hadn’t been aware of the problem of slipping brass loops at all when, a few years ago, some of the strings in a harpsichord used by my ensemble suddenly gave up keeping their pitch. There seems to be a dual explanation for my lack of experience: 1) The brass sections in my own instruments are strung in beryllium-copper, a material that has characteristics in some ways closer to early brass (for example it only stretches very little before settling, and it sounds pretty nice from the start on). As an aside, beryllium copper looks like copper-bronze (which many people find useless – I have no experience with it) but is something else nevertheless. What matters here: reasonably well-made Beryllium copper loops just don’t slip. 2) One of the things apparently typical to brass loops is that they begin to slip after years and years of behaving nicely. At the moment the trouble started, the instrument in question was about ten years old.
In any case, I went through all the steps of “what now?” solutions that, as I learned recently, make the entire harpsichord world happy.
I took off the string and tried to wind the loop tighter. It snapped.
When winding the loop for the new string, I tried to make the double helix tighter than usual in order to avoid the new string from slipping as the old had done. It snapped.
Fiddling around, I finally created a loop that didn’t slip. I left the problem behind me with the slight bewilderment of someone who just solved a Windows crash but doesn’t really know how.
So in a way I was grateful when the topic came up on the list. Some people have a theory: modern histori-surrogate brass slips, the old brass didn’t. Other hpschd-listers have a solution. If everything else fails they drip crazy glue right into the slipping loop.
I can’t comment upon The Theory, I’m no metallurgist. However, a new brass string leaves a deep black trace behind on a leather strop or a micro-fiber cloth. This indicates, to my practical mind, that its surface might be contaminated with grease or other residue from the manufacturing process. Either might add to the string’s slipperiness. I have now started to wipe all new strings before making the loop very thoroughly and I’ve had no problems since then (let’s, however, wait another ten years)
I was at first a little sceptical about The Solution. I don’t really believe in the long-term stability of crazy glue. But perhaps I’ll have to admit that the idea of, with a simple drop of goo, instantly stopping that enraging continuous dropping-of-a-semitone-whatever-one-does that some of these strings develop is very tempting.
Some people recommended the so-called German loop, as known for example from the harpsichords by the Klop firm. If made properly, the German loop doesn’t slip. On his website, Carey Beebe shows great pictures of both the German loop and a nifty “secure loop” (click through the arrows of the “technical library” until page VI). On page V of the same site, we can find a picture of the standard kind of loops that I normally make. The only difference is that I actually make them free-hand. Here’s how:
Place loop end in non-dominant hand; hold both string and the short string end tight in dominant hand at the place where the double helix will be; begin twisting each (or only one) hand as felt appropriate; pay special attention to the two string ends twisting around each other, as opposed to one staying straight while the other one gets twisted around; stop when almost done; finish off by winding string end a few times around the string to prevent spontaneous unwinding.
This technique works really fine; only the lower strings of post-1800 fortepianos and the thinnest brass diameters are tricky, for opposed reasons. The thick ones are fat and stiff and make one’s fingers hurt. The thin ones are springy and brittle and either don’t want to wind up properly or tend to snap.