Ongoing discussion of VPiano and PianoTeq on another forum (Page 2 of 2)

I firmly believe that the velocity at which the hammer hits the string is all that matters - of course if the hammer has hit the string only a fraction of a second previously, then the sound of the hammer hitting an already vibrating string will be different than that of a hammer hitting a string at rest.

Consequently, if all that matters is the velocity at which the hammer hits the string, then the "loose" connection between key and hammer doesn't come into play.  In fact it is precisely because of this loose connection that the final striking velocity is all that matters.

We don't have any where near the control over our piano strings as do guitarists, violinists, harpists, etc) because they are in direct contact with the strings with very sensitive and tactile fingers.  Not that our fingers aren't very sensitive, but the action isolates our fingers from the strings.

On the matter of the entire velocity path of the hammer, I really don't think it matters - the striking velocity is all that affects the sound (except as already noted above about hitting already vibrating strings).

If the hammer isn't in the resting position, the key re-activates the movement of the hammer, and once in motion, there can be no further control over its motion - it simply flies into the string.

If someone is familiar with the Yamaha system, it would be enlightening to learn what parameters they measure.

For the preliminary rounds of the Minnesota International Piano e-Competition, contestants play a Yamaha Disklavier piano - the midi information is then transmitted live to another Yamaha Disklavier piano far away where the judge(s) listens to another Yamaha piano which plays the contestant's file.  If it's real enough for judging world class talent, then it's likely real enough for most of us.

http://www.piano-e-competition.com/

Incidentally there are some very good renditions of many classical piano pieces that can be DL'd in midi format for no charge.

Glenn

The only "thing" a hammer can transmit to a string is energy.

Energy is a function of velocity and mass - nothing else.

The equation for the energy of a moving mass is "one half the product of mass times the square of the velocity".  This is from classical mechanics.

Acceleration is simply the change of velocity with respect to time, but when the hammer hits the string, it matters little if the hammer is accelerating or decelerating.

As a matter of fact, once the hammer escapes the influence of the key (and it does - hence the term "escapement"), the velocity decreases ever so slightly due to frictional losses, and in grands because their hammers are being slowed on their upward path by gravity.  But this is not significant as the travel distance is not long.

It is still widely believed by many pianists (most likely because that's what they've been taught - keep in mind that not many pianists are physicists), that they can influence the tone by how they stroke the key.  But the only thing that changes the tone or timbre is the velocity of the hammer when it strikes the strings.  Harder strikes (velocities) result in more harsh overtones.  This is probably more effective in the bass with longer strings that are copper wound which renders them less like a bar and more like an ideal string (an ideal string has no stiffness whatsoever).

A vibraphone's bars are relatively much stiffer, and this creates relatively more odd harmonics.

Glenn

Correct me if I'm wrong, but since there is an escapement in the action of an acoustic grand, there is a physical limit during a very slow keypress, where the hammer will be loosed and if the key velocity is below a certain threshold, the hammer will fall away (stop accelerating) without striking the string. 

Ergo, Joshua's system is unnecessarily complex and all we're really talking about is trying to impose more control at lower velocities.  By depressing the key part way and then starting to actually key the note, the player is simply decreasing the efficiency of the lever system, as in some "soft pedal" actions which bring the hammer closer to the strings.

1) Key depressed from top of keystroke to keybed in one continuous movement:  Potential energy stored, transferred to the lever, converted to kinetic energy when hammer is thrown.

2) Key depressed part way, held, then depressed again:  LESS potential energy stored, transferred to the lever, coverted to less kinetic energy and hammer thrown less forcefully.

If force applied in situation 1 and situation 2 are identical, the sound will be identical in timbre and volume.  If force 1 != force 2 then the timbre and volume will be different, but due to the non-linear nature of hammer hardness, they won't necessarily vary by the same amount, which would explain how the "same" volume could have different tonality.

Or, it's like when I think about cotton wool and my mouth goes dry and finger-ends can feel it.  I.e. it's all in your head.

Neil

The energy of a hammer (as it hits a string) is solely dependent on its mass and velocity - acceleration isn't part of the equation (first and second year engineering physics - refer to previous post).

Always keep in mind (because of the escapement action of pianos) that once the hammer escapes its connection to the key, we have no influence over it at all.

Oddly, many pianists that absolutely rely on this escapement feature, seem to forget what it means - it means that when the hammer flies to the strings, we no longer have any control over it until it returns to be re-activated by the key.  Sadly most piano teachers are not physicists either, and the myth of the control over tone lingers.

This is an interesting discourse (that may or may not convince some with long held beliefs):

http://www.nybooks.com/articles/214

Demolition of this myth is long overdue.  However, I know neither I nor others will ever convince many pianists - beliefs are extremely hard to change.

(Of course if the hammer hits the string at higher velocities, the tone will be harsher, in part due to a louder noise of the hammer hitting an object (if you take a piano hammer out and hit a table it makes a noise), and of course the previously mentioned larger component of dissonant harmonics.)

Glenn

PS - I do envy guitarists and other musicians that interact directly with the strings/reeds/mouthpieces of their instruments - they can do all sorts of shaping and changing of the sound.  Perhaps the unfounded belief of pianists is rooted in envy; I have it.

As an afterthought, my mother was not only an accomplished pianists, she was a registered music teacher.  She also taught me that my touch could affect tone - however, later when I became an engineer (applied physicist), I realized that the reason I couldn't affect the tone was based on a sound understanding of physics, not my lack of touch.

G

This is exactly true!  And it's something that is reproduced quite authentically on my RD-700GX.  However I have found that NONE of the software-based pianos work this way without some tweaking to the curves and even then it ends up feeling a little "fake" if it even works at all.

For example, I can't seem to get Ivory to NOT sound a note at all no matter how lightly I press the key.