Laurent, I hope that you have a chance to see a Boesendorfer SE piano,
and to decide for yourself about the capability of this technology.

The SE mechanism was designed to faithfully reproduce a performance
recorded on _any_ piano equipped with the same system.  A self-
calibration procedure assures that the hammers in all pianos respond
identically at all possible velocities, and a companion manual procedure
is performed to verify that all of the pedal actions are identical
amongst SE instruments.  The positions of the keyframe shifter and the
damper-lifting tray are recorded and reproduced using linear position
transducers.

Hammer velocity is measured by precision shutters passing through the
light beams of opto-interrupters.  The solenoid velocity is measured with
a permanent-magnet linear transducer.  Hammer-velocity commands are
presented to the "key motor", which consists of a large solenoid and its
velocity transducer; the current to the solenoid is adjusted by a
feedback controller to yield the commanded velocity.

Since the solenoid (hence the key) is velocity-controlled, the varying
friction inherent in a piano action has little effect on the player
mechanism.  It is possible to depress every key reliably without any
sound produced, by issuing the command to strike the key with zero
velocity.  The SE mechanism indeed performs this action: the key goes
down, the damper rises, and the hammer swings up to the let-off position
without striking the string.  All 88 keys (97 keys in the *big* Boesen-
dorfer) will successfully pass this test, every time, after calibration.

The performance capabilities of the SE mechanism are tremendous; so is
its cost.  The solenoid action stack is so heavy that an automotive
transmission jack must be used to safely install it !  The system was
designed in the mid-1970s, yet after twenty years it still represents
the ultimate standard of performance against which all other reproducing
systems may be compared.

Best regards, Robbie Rhodes