I had someone machine down the piece
of old piano soundboard to just over an
eighth of an inch. It is necessarily thin, but
a l t h o u g h t h e w e i g h t o n i t i s s p r e a d t h r o u g h
the bridge which spans a large area, the
pressure needs to be carefully regulated.
There needs to be enough pressure to
transmit the sound and to prevent each
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the tangent when played. Being thin, all
soundboards have bars to support them;
I had played the violin and knew these
have a sound post. Particularly as my
soundboard overhung, I combined the
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in place with the bridge attached and a bar
underneath it which would strengthen it
and perhaps spread the sound. With the
soundboard being so thin and soft I used
two tiny screws to help secure the glued
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the bridge.
The science of bars under soundboards
is still somewhat debatable and maybe
bars shouldn’t be attached to the bridge
— certainly they should not go too near
the edge of the soundboard and so limit
its vibration.
Getting there
I positioned the top three keys beneath
where they would go, tracing the outline
of the overhanging keyboard on the
top three.
I then cut away in that area as much
of those as I felt was safe and adjusted
their balance. I calculated the minimum
height of the tangents required to reach
past the support and up to the string at
the level of the bridge when the note
was played.
I cut a recess in the frame to allow the
back end of the keys to rest on a strip of
felt there, tapering above to hide the ends.
$WÀUVW,FXWWKHWDQJHQWVIURPDVWULSRI(^3) ¼ 16 - by (^1) ¼ 16 -inch brass. This was tapered at
the top where it contacts the strings and
sharpened at the bottom so that I could
push it into the back of the key. Although
the forces are not great this was not very
satisfactory and I replaced them with
(^5) ¼ 32 -inch brass rod inserted into the key
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space where the paired strings were close
together, particularly at the treble end.
Nearly ready to go!
The finishing touch
Knowing that many soundboards are
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on mine and obtained a reasonable
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I used satin polyurethane.
Hitch pins, bridge pins,
and tuning pins;
Necessary slight horizontal and vertical
string angles.
I spaced out hitch pins along the back
of the frame according to my scale
diagram. Taking a line from the hitch
pin over the relevant pin in the bridge I
Above: Frame design to
support overhanging
soundboard
Right: Post supports
overhanging soundboard.
It is outside the soundbox,
so is not a sound post.
Note holes of relocated
balance bar pins