From his reference sources Dave Vincent gave the composition of Hoyt
metal as:

  Hoyt metal -- two ply, tin coated, 84% lead, 10% tin, 6% antimony

A principal factor in designing organ pipes for commercial consumption
is cost.  This was especially so as electronics began offering competi-
tion for church dollars in the 20's and 30's.  It became common to
offer metal pipes with low tin content because tin was much more
expensive than lead.  Older Dutch and German pipes were typically 90%
tin and 10% lead.  These high tin pipes had a bright sound and lasted
forever in the absence of mechanical catastrophe.

American pipes of the early 1900's were made with increasing lead
content.  Organ builders soon discovered that the pipes sagged under
their own weight so they added antimony as a stiffener for the high
lead alloy.  Organ builders soon discovered that high lead pipes began
to crumble from simple air oxidation.  Lead would oxidize at the grain
boundaries and the alloy would loose almost all of it's tensile
strength.

Knowing that high tin content pipes never oxidized, pipe builders began
to coat finished pipes with tin to prevent oxidation of the underlying
structure.  This was only partially successful.  For many reasons the
tin coatings became porous and oxidation of lead continued through the
tin coating.

The idea of a two-ply pipe metal has been abandoned for many years for
the above reasons.

Bill Finch

 [ May I conclude, then, that "two-ply" is a simply a highfalutin'
 [ organbuilder's term for tin-plated, as Dave Vincent suggested?
 [ That's even thinner than two-ply toilet paper!
 [
 [ I thought that any layer of material measured in micro-inches
 [ thickness is called plating, and if it's layered thicker than
 [ that it might be a called a coating.  I suppose we will someday
 [ see labels on furniture saying "two-ply mahogony", when it should
 [ actually state that it's "mahogany plated".   :(   -- Robbie