[ Most problems encountered in restoring pianos lie outside the realm
 [ of MMDigest, which usually deals with just the player problems.  But
 [ here's a situation where the stringing scale is unique to a player
 [ piano.  -- Robbie

  Bass String Diameters in Mason & Hamlin Ampico Pianos

Many string scales exist for the Mason & Hamlin piano, particularly the
Model A (5' 8" length).  This author has heard of or seen about ten
different scales on the RA piano [fitted] with either the Ampico A or B
player system.

One interpretation of this state of affairs is that American Piano
Company was trying to improve the sound of that popular size piano in
the years 1924 to 1929, especially in the bass section.  I believe that
they succeeded, with the delightfully lush, superbly resonant A9 scale.

Decades later, many of those instruments needed to have the bass
strings replaced, because of tone-robbing effects of atmospherically
induced corrosion of the copper windings (to adjacent turns) on the
bass strings.

Unfortunately, some of the commercial firms that specialize in
supplying replacement bass strings do not know that the M&H A scale
incorporated at least eight variants (differing steel and copper
wire diameters) among the bass strings for those instruments.  This
can and does give rise to circumstances where new bass strings do
not sound quite right, and no amount of mechanical (strike line) or
hammer-related "adjusting" (needling) corrects the situation.  The
explanation for this follows below.

The Mason & Hamlin designers were very knowledgeable.  Each
subsequent string scale for the Model A reflected a tonal refinement
upon the previous edition.  The steel and copper wire diameters were
incrementally adjusted (along with soundboard thickness variations)
to realize steadily "improving" overall tone, especially in the bass.

This is characteristic of the nature of empirical design.  In essence,
the bass strings were interactively matched to the respective
soundboard.  If the bass strings are replaced subsequently, the
diameters of the steel core wires and the copper windings must be
properly matched to the originals.  Otherwise, the piano will not
sound quite right.  Why?

Inadvertent or deliberate changes to the diameters of the steel core
wires in the bass during a piano restoration will adversely affect the
intended tensions of those bass strings.  The now incorrect tensions
in the affected strings will change the downbearing on the bass bridge.

This can produce significant deviation from the original design.  If
too many bass strings are affected in this manner, this can result in
a mechanical distortion of the original intended shape (empirically
designed vertical profile) of the soundboard.

Because the non-wound strings in the tenor and treble sections are
rarely replaced with incorrect diameter wires, those sections of the
piano sound fine.  The original diameters of those strings are usually
clearly marked on the pianos plate.  In the bass section, there is no
corresponding wire diameter marking, which introduces replacement
ambiguity.

Unless the original bass strings are duplicated, or the bass string
supplier provides the correct replacements for that particular scale
of the Model A piano (e.g., A4, A5, A6X, A9), the tonal character of
the piano will be noticeably altered in an unpleasant manner.  Have
you ever experienced this problem?

I ran into this problem about 20 years ago with RA 41164, a Mason &
Hamlin Ampico B piano with the A9 scale.  Of the 52 wound bass strings,
about half of the commercial replacements (sadly, not duplicates) had
incorrect steel wire diameters and consequent incorrect copper wire
diameters.  When the root cause of the problem was identified, a second
replacement set (duplicates of the originals, which I had saved) of
bass strings was installed.

What a delightful world of difference in the tonal sonority of the
piano!  All the research expended to pinpoint the difficulty was
worth it.  The moral of this story, which may apply to pianos of other
manufacturers, might be entitled "Save the Original Bass Strings."

For the A9 scale, the deepest (lowest frequency) bass notes (8 of them)
have double wound bass strings.  To my initial surprise, the original
inner windings consisted of iron wire, definitely not copper.  Because
copper is denser than iron, this material difference should be taken
into account when duplicating those bass strings.

The diameters of the "inner winding" wires in those few strings are
small compared to the diameters of the corresponding outer copper
winding wires.  For example, with the lowest bass note of the A9 scale,
the original diameter of the inner winding iron wire is .018" and the
diameter of the outer copper winding is .077"; the diameter of the
corresponding steel core wire is .059".  The tonal effect of this
difference in materials (copper versus iron) is secondary compared
to errors in the diameters of the steel core wires themselves (two or
three thousandths of an inch is all it takes).

Why was iron used for the inner winding wire?  Was this common practice
for some bass strings in 'mid-size' pianos made by other manufacturers?

Is the iron inner winding wire in the deep bass section peculiar to
Mason & Hamlin in the Model A?  My guess is that iron was used to reduce
the long-term effects of corrosion.  That is, copper would corrode
against copper faster than copper on iron.  Would someone in the MMD
community please help answer some of these questions?  Please respond
to MMD or send me an email at the address below.  Thank you.

Bill Koenigsberg
Concord, Massachusetts
billkberg@comcast.net.geentroep [delete ".geentroep" to reply]

 [ Early this year Bill helped MMDers George Epple and Ralph Nielsen
 [ determine the original string scale for George's Ampico B.  George
 [ wrote to me, "This particular 'A9' scale was seemingly only used in
 [ a very few (possibly less than 30) early Ampico B Mason & Hamlins."
 [ -- Robbie