>What I really want to know is what is beating against what, and while I >really really really didn't want to speculate, the hypothesis that seems >most convincing to me so far was posted by John Musselwhite: > >"Would those problematic single bass strings have LMFs [longitudinal mode >frequencies] that are either unstable or out of tune with the rest of the >string?" Out tuning the last couple of days, doing too many pitch raises, and paying specific attention, I have some observations. I don't believe longitudinal mode frequencies are it. Pulling a string up from a half semitone down (or at least over a considerable pitch range) I sometimes hear a high pitched whistle at a certain pitch that goes away as the string comes to pitch. Or it appears as the string comes to pitch and I'm stuck with it. I think these are longitudinal mode noises, and the beating is something else. One of the pianos I tuned was one I had rescaled. Some of the monochords beat, some not. The beating of individual wrapped strings is, I think, more like what David Love suggests. Minor stiffness and mass differences within the string. If a section of any given string is a bit stiffer than another section, or a bit different in mass, it would surely affect the partial structure. It wouldn't take much necking down of copper wrap, from slightly varying wrap tensions as the string was made, to affect mass distribution. This makes sense to me, especially considering that most of the beating monochords I've listened to in the last two days have beat at slower than two per second. If that's the case, then getting rid of these beats for your customer will consist of replacing beating strings one at a time, quite possibly repeatedly, until they are all clean enough to suit - or the customer is tired of paying for the process. Then we can find out if these beats develop in previously clean strings with the passage of time. Ron N
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