<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; "><DIV><DIV>On Jun 7, 2007, at 10:15 AM, Ron Nossaman wrote:</DIV><BR class="Apple-interchange-newline"><BLOCKQUOTE type="cite"><P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">Bridges are in the Dampp-Chaser environment as well as soundboards.</FONT></P> </BLOCKQUOTE><BR></DIV>Hi Ron,<BR><DIV><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN>Thanks for the specifics. They are certainly persuasive on the surface, though there are a couple issues I'd have to sort through. It isn't necessarily just length change in terms of how far the string goes from tuning pin to hitch. There is also a speaking length component. The two are related, but one without the other (for purposes of analysis) is incomplete. Where the bridge pin ends up relative to the front termination is an open question, not one easily measured. One of the Fandrich's (I forget which, but think Darrell) wrote about pitch change due to elongation of the bridge toward the tenor end about ten years ago, citing speaking length change as a major factor. I didn't entirely buy the argument at the time, as it seemed that increasing the distance from tuning pin to bridge pin was causing a rise in pitch (setting aside the tension component). Longer speaking length means lower pitch to me, other things being equal (if they ever are). Still, the general principle of changes in speaking length caused by wood swelling and shrinking makes sense as a factor to consider. </DIV><DIV><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN>Soundboard movement in response to humidity change isn't just up/down. The position of the bridge relative to the front termination may change due to whatever is happening to the board. A bit sideways, a bit back or forth, a bit of change in cant. It certainly isn't as simple as up and down, increasing/decreasing bearing (and, hence, distance from a to b, and, hence, tension). </DIV><DIV><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN>You really think the moisture transfer from the bottom of the soundboard into (and from) the bridges of a grand is enough to stabilize the bridges to a significant degree? That's where my mind can't get away from the soundboard being a fairly large contributing factor in humidity induced pitch change - the degree to which a full Dampp-chaser system, or just a heating rod (or two, with enough wattage) and humidistat really take a large portion of the pitch change away. I've measured RH on top of the board many times, between plate and board (as far under, in as undisturbed area as I can reach the instrument), and found a miniscule effect from the system beneath (maybe 2% above/below ambiant, rarely as much as 5%). I would think there would have to be more moisture transfer to and from the relatively static air above the board if it was true that significant moisture would migrate through to/from the bridge, and particularly to the top of the bridge, where, presumably, most of the effects you describe are taking place. That's got me stumped. Maybe you have worked through it. It's something that could be set up as an experiment and measured, given the right measuring tools.</DIV><DIV><SPAN class="Apple-tab-span" style="white-space:pre"> </SPAN><BR><DIV><DIV>Regards,</DIV><DIV>Fred Sturm</DIV><DIV>University of New Mexico</DIV><DIV><A href="mailto:fssturm@unm.edu">fssturm@unm.edu</A></DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV></DIV></DIV></BODY></HTML>