No downbearing ?

[Cy Shuster]

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For Christmas I received Arthur Benade's book, "Fundamentals of Musical =
Acoustics" (Dover, 1990).  It has a thorough coverage of sounds in a =
wide variety of instruments, from drums, brass, woodwinds, harpsichords, =
and pianos.  The math is kept simple, and the acoustics discussions are =
oriented towards musicians rather than scientists, so I'm really =
enjoying it.  He has apparently consulted with instrument manufacturers =
of various types, so his theories are grounded in practice.  Each =
chapter ends with enough questions and exercises to use up every =
electron in the universe on this list.

On p. 331, he discusses downbearing.  Is this practice of fine =
adjustment still followed?

"...downbearing is carefully proportioned to vary along the scale of any =
properly made musical instrument.  Makers of the finest instruments find =
that the downbearing must be meticulously adjusted string by string on =
each individual piano, as a part of its final regulation.  Errors in the =
trend of the relationship among P [downbearing], Q [backscale], and the =
string tension can cause as much trouble to the overall sound of the =
piano as can errors in the stiffness and curve of the bridge, or in the =
thickness of the soundboard."

(A diagram shows the bridge, rear bearing surface (what's the right =
term?), and hitch pin.  The distance between the bridge and rear bearing =
surface is labeled "Q" (it's a muted backscale in his diagram).  A level =
line is extended from the bridge towards the hitch pin.  Its height, as =
it crosses over the rear bearing surface, is labeled "P".)

"Notice that the downbearing is not simply a matter of getting adequate =
contact between the bridge and the strings; the string tension acting =
together with theeoffset on the bridge where the string runs zigzag past =
two steel pins is already quite sufficient for this contact..."

--Cy Shuster--
Rochester, MN

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