Disklavier

I probably should have explained a little more about the "escapement" 
mechanism of a piano action being different from just a laser shutter 
breaking a beam measuring  an electronic value.  An electronic key can 
measure all numbers, 0 to 128 for velocity.  All data recorded on an 
electronic keyboard with a tone generator that is well designed should 
record and playback as accurately as recorded.

Like you said, the DKV Pro duplicatesas close a possible, a piano 
performance.  This is different than an electronic keyboard performance.  
Why?

If you look at how a piano action is adjusted in slow motion, you would see 
that depressing a key moves a stick (jack) under a leather knuckle mounted 
on the piano hammer lever.  This in turn sends the piano hammer flying off 
toward the string.  However, the direct force of your finger upon a key is 
removed before the hammer hits the string!  This is called escapement, or in 
piano tech terms, let-off.  No matter how hard you hit a piano key, the 
total amount of the force is never sent directly to the strings.  Same 
principle works for how soft a piano note plays.  Because there is friction 
between the leather knuckle and the top of the jack, there will always be a 
certain amount of energy required to overcome this.

Hammer sensors and key sensors measure the travel of the piano you are 
recording on and generate a set of numbers.  Take those numbers and play a 
different piano, you are dealing with different amounts of friction and 
piano action adjustment.  Also, the position of the laser shutters on the 
hammers is BEFORE the hammer reaches let-off.  No matter what that number is 
it is overwritten by the mechanical let-off ajustment - which is usually set 
between 1/8 and 1/4 inches away from the string.

Bob is right in that a mechanical piano action plays as low as 20.  You 
certainly would not want it to play harder than 100 (and I think that is too 
loud)because the solenoids will pound the keys much harder than they are 
designed to be played. In other words, the dynamic range of a fine piano is 
not 0 to 128, but more like 20 to 100.  The velocity measurement in MIDI is 
not affected by friction of a leather knuckle or the escapement of the piano 
action.

This Disklavier Pro is the best thing out there for recording live piano 
performances.  That it will not record MIDI numbers between 0 and 20, and 
100 and 128 is really of no consequence.



Carol Beigel
crbrpt@...





>From: James Fry <linx@...>
>Reply-To: disklavier@yahoogroups.com
>To: disklavier@yahoogroups.com
>Subject: Re: [disklavier] Question about midi out velocity
>Date: Sat, 8 Mar 2003 14:41:16 +0000 (GMT)
>
>I'm not sure that's quite the case - the way the hammer speed is measured
>is basically exactly the same as how a digital keyboard measures the speed
>of the key.
>
>On the disklaviers there are beams that are broken and unbroken by the
>hammers. Since the distance between the beams (on 4 position models) and
>thickness of the hammer / shank is known, it's possible to calculate the
>velocity from the length of time it took the hammer to travel between the
>beams. I believe the extra sensor on each key is used to detect the
>release of a note more than anything else, but it is feasable it is also
>used in the velocity calculation. On the models with continuous position
>sensing, things are obviously slightly different.
>
>On a digital keyboard there are two contacts under each key very
>close together and the time it takes for the two circuits to be made is
>measured and velocity calculated in the same way as the hammers on a
>disklavier.
>
>I'd have thought the most important thing was to capture the performance
>as accurately as possible. If the instrument currently can't play back
>that accurately, so what - the chances are future instruments will be able
>to.
>
>If Yamaha are limiting the range of velocities output by the disklavier,
>they are reducing the expressiveness of the instrument - the full scale
>should be used, and then rescaling of the velocities used if necessary at
>playback time. Midi is regularly criticised for its lack of controller
>expressiveness; if the disklavier only handles velocities between 20 and
>100 (about 60% of what MIDI is capable of) then no wonder a lot of people
>don't like their performances being recorded on it.
>
>I think playback on the disklavier is a different matter - the only way to
>get more expression here is to use solenoids with faster response and more
>power, which I beleive the Mark III Pro series of grands have.
>
>Regards,
>
>James
>


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