Disklavier

In the interest of truth, not of nit picking, I would like to 
respectfully point out that the "Keyboard Measurement" done in the DKV's 
Maintenance Mode benefits reproduction accuracy, but does nothing for 
recording accuracy.

In the recording process, optical sensors on the Key Sensor Rail detect 
which key is depressed, the time of a Note-on, and the time of a 
Note-off.  Optical sensors on the Hammer Sensor Rail measure the speed 
of the hammer just before impact.  These sensors are relatively fixed 
geometrically and do not have automated calibration routines in the 
Maintenance Mode nor are related data values entered into tables.

In the reproduction process, the DKV reproduces hammer velocity by 
applying to the solenoid a driving pulse of appropriate duration--a 
short pulse for a low velocity note and a longer pulse for a higher 
velocity note.  You will sense from your playing of the instrument that 
your fingers must apply greater force to the bass keys than to the 
treble to achieve the same hammer velocity.  That is because the bass 
hammers are more massive than the treble.  Further, each hammer pivots 
on a wrist pin. Depending upon the tightness of the pin in its joint, 
more or less energy from a keystroke is wasted in heat and doesn't 
contribute to hammer velocity.

To compensate for the different masses of hammers and different amounts 
of knuckle friction (as the joints wear or change with humidity), the 
DKV keeps a data table that enables the controller to apply the correct 
duration of pulse to the solenoid depending upon the desired hammer 
velocity and the characteristics of the keyboard escapement for that 
key.  The Keyboard Measurement process, performed in the Maintenance 
Mode, updates that data table.

Before performing the Keyboard Measurement, the keyboard escapement 
should be brought into good regulation. If its regulation is out of 
tolerance (as far as the DKV is concerned), you will not get the OK that 
Carol described, but rather the key numbers that need work.

To recap what I've said, here is a quote from Yamaha's maintenance 
literature that describes what is going on during the Keyboard Measurement:

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The other program, or electronic tool that we
use is called \ufffdMaintenance Mode\ufffd. Here the
piano regulation is \ufffdmated\ufffd with the electro-mechanical
system. Calibration takes place to adjust the playback system to the 
present condition of regulation.

In Maintenance Mode - Keyboard
Measurement, each solenoid is energized
with a varying, but precise pulse width. The
actual hammer velocity is then measured and
stored in a matrix or table. The resultant table
is used when the Disklavier plays back a
song.

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-- 
Robert Welcyng
Anchorage, Alaska