Re: moisture factoid, was Re: Organ Pipes

[Mike Smith <mike@COMET.UCAR.EDU>]

> Rick Tarara wrote:
>
> > You only have to do a calculation to see that the tuning effect lies
almost
> > entirely with the temperature dependence of the speed of sound in air.
The
> > expansion/contraction of the instruments contributes minimally.
> >
> > Rick
> >
> > *********************************************************
> > Richard W. Tarara

Rick is correct, but as a one-time orchestral musician, may I suggest that
when it comes to "tuning"--as opposed to an overall pitch level for all
instruments in the room as determined by the local speed of sound--is
actually far more complex.

Tuning varies by individual instrument and section in the orchestra.
Strings--gut certainly, but even metal-wrapped--expand as the temperature
increases (under stage lights, for example); so the tension decreases and
the pitch drops, hence the necessity for retuning onstage as instruments
warm up.  To make matters worse, sound boxes on the strings expand
differently with temperature and humidity changes than do the strings
themselves, depending on the instrument size (violins, violas, celli, and
basses) and, to a lesser extent, the condition of the wood, which varies
from instrument to instrument, as well as from section to section.
Woodwinds have different expansion characteristics than do brasswinds.
Tuning compromises for instruments with overblown octaves (most woodwinds)
differs from the compromises for overblown 12ths on clarinets.

That barely skims the surface, but you get the general idea.  At least the
historic problems with timpani tuning are better now that all but the Vienna
Philharmonic have abandoned calfskin heads.

Cheers,

Mike Smith
Boulder, Colorado