Hupfeld instruments are rarely simple, though they work beautifully if
set up properly.  Like Rolls Royce, Hupfeld seem not to have believed
in simplicity for its own sake!

On Solophonolas the drive is held in play mode pneumatically when the
tempo lever is in the sector with tempo markings.  When it is moved off
the scale to the right, silent fast forward occurs; even further to the
right (extreme left on some installations I've seen) is silent fast
rewind.

Earlier Solophonolas have subduing levers for both bass and treble.
They are squeezed toward each other with the left  forefinger and thumb
to subdue, the remaining fingers being able to press the sustain button
on the left.  Later models don't have the swing-up control panel, but
fold out levers and rounded sprung drop-down tabs behind a 10" wide
panel in the centre of the key slip.  The very latest, 1930 something,
only have one lever to subdue both bass and treble.  (Shame).  Some
later models, which don't feature the tram-handle una corda lever, have
a soft button between the subduing levers; on some, the soft (hammer
lift) rail rises when either subduing lever (or just the one) is
squeezed to pp.

The sustain and soft pedal mechanisms use curious designs where a
primary valve closes a small pneumatic which lifts a large adjustable
disc secondary.  They look unduly complicated but when they are set
correctly they operate at just the right speed without chuffing or
banging down the dampers.  Hupfeld seem to have known how to achieve
the result they desired.

Solophonolas with separate bass and treble subduing levers have two
separate bass and treble regulator pneumatics for the Solodant, unlike
Themodist Pianolas which, good as they are, have just one.  Inside are
differential valves, double sliding sash or roller blind, rather than
simple shaped throttles and a knife valve.  Each regulator has a spring
adjuster with a knurled locking screw which on older grands is accessible
just behind the bass and treble legs.  It's worth remembering that
as on the Pianola this adjustment is intended only to stop pianissimo
notes from just failing, and not to make the instrument play easily and
loudly with one foot!

The Solodant valves are smaller versions of the sustain and soft valve
systems, the exposed leather nut atop the secondary valve stem being
used to adjust the timing of operation.  Again, on older grands they
are accessible just inside the legs, and can be set to work perfectly.

The vast reservoir pneumatic (under the tail of grands) has a large
steel bar 'spring' on top whose stiffness can be adjusted (after
removing the reservoir) by the position of its final fixing screw.  The
spring carries a large threaded dowel accessible under the piano which
comes up against a fixed stop.  By adjusting this spring appropriately
sudden crisp accents can be easily achieved with the merest dab on a
pedal without compromising the subtlest pianissimo playing.

I have come across a few instruments where, fitted on the underside of
the tempo regulator pneumatic, are two small tempo compensating
pneumatics, fed from their respective Solodant secondary.  By
compressing momentarily an adjustable spring they eliminate any tempo
hesitation caused by strong accents, though earlier instruments without
this feature don't hesitate if regulator and transmission are set up
correctly.

Various tracking mechanisms are found, manual and automatic.  My
Roenisch grand seems to have been manual, then had a 65/88 tracker bar
with adjustable ears fitted.  At first this seems to have moved a
rocking roller below the tracker bar and later the top right hand
clutch.  While this may indicate something about Hupfeld's development
policy, it speaks volumes for their famous after sales care.  Owners
seem to have been fiercely loyal.

Finally, later models have the most impressive mechanism for making
the pedals ooze out of or self-efface into the slimmest pedal-box/lyre
at the deftest movement of a lever just below the key bed!

Paddy Handscombe
Wivenhoe, Essex UK.