This is a multi-part message in MIME format. ---------------------- multipart/mixed attachment ------=_NextPart_001_01BC_01C55E42.B4F402B0 I'm seeing some strange pitch drops in individual strings, and I can't = figure out why. First, the history. This is a 1974 Yamaha C3, in pretty good shape, in the large band room = of a community college, with central HVAC. No D-C on the piano. Three = weeks ago, we moved it overnight to two different off-campus locations = for the spring concert series (half an hour ride in a pickup truck each = time -- yikes! I covered it up, but still...). It's had five tunings = in the last month, and I've recorded humidity each time. I use TuneLab = Pro, and used the same stored tuning each time. The series ended May 1, and I tuned it just before that concert. It = survived the concert sounding good; no slipped unisons. It's been in = the same spot for three weeks, uncovered, lid down. Now, the mystery. On Tuesday, they asked me to tune for a recording the next day, = mentioning that a few unisons were out in the top two octaves. I = measured all the A's before I tuned (as is my habit). A4 and below were = right on, except A1 and A2 were up about two cents (humidity is rising). = A5 was up 3c, A6 down 6, A7 down 3. I noticed that in many treble = unisons, one or two strings would be way off: either a string would be = right on, or off by a considerable amount (is it my string-settling = technique?). I also noticed that many strings would move a lot if I = pounded on them, before touching the pin. I worked hard on those top = two sections of the plate, making sure every string was well settled, = and wouldn't move. Yesterday, they called me back to tune their other piano, and also = mentioned that the top two octaves were out on the Yamaha again (!). I = checked it, and A2 and below were spot-on, as were A6 and above. But in = the middle three octaves, a dozen notes had one, two, or three strings = off by two or three cents (A4 was down five cents!). All but one were = flat. Again, either a string would be exactly in tune, or off by a lot. = I checked the pitch of every string before I began to tune, and = chalk-marked the tuning pin of each string that was out (for next time). = =20 They did mention that they turned off the A/C in the room for the = recording (because of noise), and then fired it up full blast during = breaks. Here's the temp/humidity record (graph attached). Humidity was lower in = the two off-campus locations, and has climbed steadily upwards. 4/10: 72F, 42% 4/17: 68F, 32% (off-campus) 5/1: 68F, 39-41% (back home; last concert) 5/17: 72F, 44-48%RH.=20 5/20: 72F, 55% By the way, the other piano didn't exhibit this symptom of individual = strings falling, and others staying right on. This is really the heart = of the mystery to me. My experience with pitch swings from humidity is = that it affects strings evenly. The other piano is a D in a different = room, with similar humidity, also last tuned 5/1. It was sharp a few = cents evenly across the middle, dropping down to -10 in the top octave. = Maybe it is my tuning lever technique? I usually finish a string by = coming down to pitch, to make sure the pin has no residual torque; maybe = I'm leaving some tension in the front string segment that settles back = to the speaking length during play, or humidity changes? In writing = this history, I notice that the top two sections that I worked hard on = Tuesday night were still fine; the problems I found yesterday were lower = down. The other possible suspect is loose bridge pins. Earlier I had noticed = a consistent drop around A6 on some strings, and found I could slightly = move a few leading bridge pins with screwdriver pressure. How this = would lead to pitch drop, I'm not exactly sure... --Cy Shuster-- Bluefield, WV ------=_NextPart_001_01BC_01C55E42.B4F402B0 An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/caut.php/attachments/41/20/5c/b2/attachment.htm ------=_NextPart_001_01BC_01C55E42.B4F402B0-- ---------------------- multipart/mixed attachment A non-text attachment was scrubbed... Name: humidityHistory.JPG Type: image/jpeg Size: 18833 bytes Desc: not available Url : https://www.moypiano.com/ptg/caut.php/attachments/c0/8e/6a/d1/humidityHistory.JPG ---------------------- multipart/mixed attachment--
This PTG archive page provided courtesy of Moy Piano Service, LLC