> From: "David Nereson" <da88ve at gmail.com> > Date: March 9, 2010 1:32:32 PM EST > I've often tuned pianos where, as I'm packing up my tools, the customer tries a few notes, and I can hear a unison or two that has already drifted. This is usually when a pitch raise has just been carried out, but not always. I'm afraid stability is an elusive goal, but we try our best. > --David Nereson, RPT Hi David, I would bet that you do excellent tunings. Unison drift certainly happens inevitably. I do want to ask, though, if you check your unisons as the last thing that you do before putting away tools. If you do this, you shouldn't have any twinges of "oops" if your client plays while you put away your tools. I don't see any reason (except for time spent) not to check unisons last. This is not intended as a criticism; just a suggestion. If unisons have drifted after a pitch raise, that usually means that I need another pass (at least a quick "clean up" pass). If you tune center strings, then left, then right (as you would probably do with a temperament strip while going up), or if you tune center, the right, then left (as you would probably do while tuning unisons as you go with a split mute), you will often find that the right string of every other unison is slightly sharp, which happens as follows (example is for split mute, but the logic is similar either way): Beginning of a pair of ascending trichord notes that start out slightly below pitch: 1) Unison 1C, string 1 2) Unison 1R, string 2 *** 3) Unison 1L, string 1 (this tuning move may slightly raise Unison 1C, string 1 by pulling wire around the shared hitch pin, but since you are tuning them together, you won't notice it as you create a nice unison between the two. After tuning, the left and center strings will remain solid, as they share a hitch pin. It may also upset our perception of Unison 1R, string 2, since the center string might have moved a tiny bit. However, Unison 1R, string 2 will be more upset in step six below.) 4) Unison 2C, string 3 5) Unison 2R, string 3 (this tuning move may slightly raise Unison 2C, string 3, but since you are tuning them together, you won't notice it as you create a nice unison. After tuning, the right and center strings will remain solid, as they share a hitch pin) 6) Unison 2L, string 2 *** (here, pulling up string 2 pulls more wire around the hitch pin, making Unison 1R, string 2 slightly sharp, which is my main point here. You have finished tuning and listening to Unison 1 for this pass, but it has been upset during the tuning of Unison 2.) If you notice this pattern (especially common if you almost nailed the pitch raise but had to pull up a bit again on that second pass), you can quickly evaluate and re-tune every sixth pin a slight nudge down (in this example, pins 3, 9, 15, etc.) which gets things cleaned up efficiently. Joe DeFazio Pittsburgh -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100310/f25eb2f2/attachment.htm>
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