Disklavier

On Sat, 8 Mar 2003, Carol Beigel wrote:
> 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.
> 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.

The escapement mechanism is largely irrelavent here though; what the
optical sensors measure is the speed that the hammer is flying into the
strings before it hits. Even if thats before "let-off" it is pretty darned
close to the final velocity of the hammer.

Anything recorded on one system and then played back on another is going
to sound system. This applies to cassettes, CD's, MP3's, samplers, digital
pianos, and pianos, but the piano should have compensation for that in the
electronics (essentially statistically normalising the data based on known
parameters of the device).

> 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.

Sure, its a different way of measuring velocity than a digital
keyboard, but there is no reason at all that it could not (and it most
certainly _should_) output a full range of velocities in exactly the same
way.

What you are saying concerns me as I am about to buy a disklavier - I can
see what you are getting at, but the possible dynamic range of piano
should bear no resemblence to MIDI velocities.

If the piano limits MIDI velocities 20-100 in the way that you say, it is
significantly reducing the resolution of any recording and introducing
very significant quantisation errors. The human ear is a very sensitive
organ - try listening to 8bit digital audio (256 values) and 16 bit
digital audio such as CD (65,536 different values). Similarly, a pianist
can reproduce many more than the 80 different volume levels that you
suggest (and many more than the MIDI ideal of 127).

Ideally the output from the piano on the very, very, very quietest notes
should be MIDI velocity 1, and the very loudest you could possibly get out
of it should be 127. In an ideal world it wouldn't be stuck in 1983 and
7-bit MIDI values - we'd be using 14/16/24-bit velocities. Note velocities
are a continuous function, and MIDI velocities are discrete and are always
going to be an approximation, but you do a lot to reduce the inaccuracy.
Limiting to little over 6-bit resolution is a bad idea.

Your argument for playback is also confusing me - surely MIDI velocity 127
should be set to the loudest that the solenoids can play without damage
occuring, not 100, and MIDI velocity 1 should be set to the quietest
audible, rather than 20?

> 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.

It is bordering on a tragedy because some of the subtleties will have been
lost which make the performance sound live. A friend owns a Yamaha P80
digital stage piano, and that is similar in that it wont output notes
below around 20 and above 100, which he finds extremely annoying when
trying to use it as a controller with Steinbergs "The Grand" etc. Perhaps
it is a design "feature" of Yamaha's ?

Regards,

James