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I know it will be far from the same but which digital piano comes closest to emulating the feel and touch of a Steinway D or any other professional piano?

ATM I need convenience, so I think digital is the best temporary solution. I am interested in the GEM PRP-800, Yamaha P140 and Korg SP-250 as they are within my price range, as well as being portable. Which model plays most like a grand? It's touch should be heavier than an upright but the keys should be more responsive. Thus you can do trills, repeated notes, glissandi etc.

Sound is important, but is secondary to touch. I've learnt that you can "upgrade" the sound using modules. If this is true then sound needn't be a problem.

What are your experiences on the above?

Thanks.

A digital piano is good for practice while keeping the sound level low, it never needs tuning, and you can move it around quite easily. But none that I know of can match the touch of a concert grand piano.

My GRP-800 just arrived in Calgary so I was up at the dealers playing with it (it won't arrive at my house until mid next week). I was able to compare the key action/feel directly with a Mason & Hamlin acoustic Grand, the GRP-800 has a similar feel, almost the same weighting (a tiny bit lighter on the GRP), solid action, very easy to play with expression, great touch. Of course you will get differences in _feel_ between different acoustics as well but in this case the subjective feel is the closest to an acoustic grand that I have yet played on. (I've sampled Yamaha, Roland, Kawai and Suzuki) The Yamaha had the heaviest action and the Roland had the lightest action.

You state that the sound was of less importance than the feel but I will at least let you know that out of all the other Digital Pianos that I've tried the GRP800 has the best sound by a long ways. GEM uses a modeled sound approach instead of sampling and the difference is amazing. It sounds exactly like an acoustic grand (I was able to compare the two side by side in the show room) all of the subtle harmonic vibrations are present, the differences in the sound based on key velocity mimics the sound of an acoustic perfectly, the pedals operate exactly as if they were operating their equivalent acoustic counterparts and impart the same changes in the sound charcteristics that occur in an acoustic when doing the same action.

In terms of build quality, the product looks like it is very well built, good fit and finish to all parts.

If you are considering a GEM pRP-800 you won't go wrong. If you want a really good review of a different brand then check out Gyro's postings on his Casio. (Gyro raves about his unit and it comes across as being a quality unit as well)

Hope that helps (I know, it was a little (lot) biased towards the GEM, but it is an excellent piano)

By the way the PRP800 and the GRP800 are exactly the same except for the cabinetry.

Voyager

voyager did you try out the yamaha CLP270/280 and CVP307/309? just wondering how they compared to the GEM.

thanks

hello tm3

I was able to try the CLP270. Nice action, good feel, including escapement. The action on the upper end Yamaha Digital Pianos is definitly much better than that found on their lower end products. In comparison to the GEM the Yamaha action does not feel quite as responsive, this may be due to the weighting of the Yamaha keys. I found that the GEM (specifically the GRP800) is closer to the _feel_ of an acoustic grand than the Yamaha is. However one thing to note here is that the CLP270 when compared to a Yamaha acoustic grand comes out feeling very close as well, just a bit heavier on the action. There is a Yamaha Grand at the studio where I take vocal lessons and the feeling on that one is close to the GEM with the GEM being just a bit lighter but not by much. (The studio Yamaha has a lot of miles on it)

Here again my personal preference would move me toward the GEM just based on the feel alone. (The sound clinches it though)

Hope this helps a bit

Voyager

If you're looking for subtle improvements be sure to try the Yamaha CLP280. I found it's keyboard to be noticeable improvement over the CLP270.

Also, I would say the feeling of the CLP280 action is toward the "light" end of the spectrum (contrary to the often heard reputation for Yamaha digitals as being "heavy").

Unfortunately, the CLP280 is not in the same price class as a P140. But, to achieve your objective you might have to increase the budget.

Yes, as noted above, you gotta remember that ammong the top end grands, the feel of the key weight changes a lot. Some grands keys feel very heavy (heavier than Yamaha digital) while some feels very light.

I prefer Kawai and Yamaha digital actions over Roland which I think is too light for imitating the grand action (but feels pretty close to vertical pianos that I've played).

I have not tried out the GEM to compare.

Yamaha P140 is not the top end of the yamaha digital, so the keys won't feel as nice as the CLP270/280, although it will feel close. You might want to give P250 a try. It will feel better than P140.

Also, the sound IS important in the action feel. You will undoubtly pick the keyboard that will have better sound, becaue it gives the illusion of better key action. It really does.

Hello,

If the portability (moving to and from places, not within the same house) is one of your top priorities, then you should compromise the action feel because Yamaha P series has GH (Graded Hammer) key while CLP series (CLP 230 and up) has much improved GH3 key.

CLP 280 has natural wood key, which has slightly better action than GH3 but IMHO not superior enough to justify the cost increase over CLP 270. Hope this helps.

TD

I agree wholeheartedly!!!

Me too. If you ever go into a (digital) piano shop and idly try a few boards without turning the power on, you will get NO idea how the instrument feels in action.

There is a strong interaction between the sound and the feel of the key!

I tend to agree with Steve and Phil. A digital piano is best judged on the playing experience rather than individual characteristics. That includes both action and sound. One will always have an impact on how you perceive the other.
So it basically means 2 things: it's best to try as many pianos as you can. And it's a very subjective matter, that depends on the kind of actionand sound you are used to, which kinds you like, etc. I will agree with everything voyager has said on the GEM ( I have a pRP800), but that's me, not you.

I found the whole experience of picking a digital piano very interesting and enjoyable, and I learned a lot about the different makes and models. Wish you the same!
Cheers,
Pieter

I know this is impossible but my question is which one is the closest at the moment.

Mike, but which grand piano?

You are assuming that all the grand pianos have same action and feel. They don't.

For Kawai Grand, I think Kawai digital feels the closest.

For Yamaha grand, I think the Yamaha digital feels the closest.

For Steinway, maybe between Kawai and Yamaha.

Again, even within the same model, they can regulate the actions differently to make it feel heavy or light.

You really have to play them to know which you like the best. Any of the top brands't top models(Yamaha, GEM, Kawai, Roland) has very good actions.

Is there a particular grand piano you have in mind?

I was fortunate enough to test out the Drake engine on a RP-800 today. There is something definitely more sophisticated about the sound compared to the Yamaha P-series or even the Roland RD700SX. My statement about sound not being crucial, was following the news of a GEM
module RP-X. If this is true then a keyboard with the right connection can be transformed into a Drake machine.

My only small criticism of the RP-800 (polished black version) was that it seemed a tad plasticky. The gaps between the keys are larger than with the Yamahas. You can almost see what's under the keys reminding you that it is a piano emulator rather than a real acoustic piano.

I think the details on the action are a bit vague.

The GRP-800 has an Advanced Graded Hammer Action.
The RP-800 has an Enhanced Real Hammer Action.
The PRP-800 has a Graded Hammer Action.

I was wondering about this. Why Yamaha didn't put GH3 on the newer P-series models.

I'll admit I don't have much experience of grands except my piano teacher's. If grands can vary widely to the extent of having an action lighter than an upright, then yes my original question would be nonsense. Pls enlighten.

If I had to choose one make it would be Steinway simply b/c it is the one most associated with concert pianists. Another one that I like is Fazioli for its bright sound.

Hi,

FYI: The Promega, RP and pRP series instruments feature a Steinway 9' and a Fazioli 10'3" as their main acoustic piano sounds.

Also, the new advanced, enhanced, weighted, graded hammer action feels great and allows for very good dynamic control over the sound. “The wording has changed over time but the RP, GRP and pRP will all share the same keybed”. Sorry for the confusion.

Best Regards,

Dave

I have recently tried an old Kawai CA840 at the shop and this model has the AWA Grand Pro action with real wooden keys which is also used in the latest CA series for Kawai digital pianos. Those keys have similar actions of real acoustic grand with the lever system and are unique compared to all the other brand. To my perception, the feel of the keys is very close to the Kawai Grand RX-2 that they had at the shop as well. Unfortunately, they didn't carry the latest CA9 or the CP205, which I would expect to have better sound.

As to the opinion of feel of the keys and the sound of the piano, I agree with many of you on that they should come together to be a good digital piano.

Mikelangeli,
Here is my digital system. I have shown it to many others on this forum who've asked similar questions to yours. I also have three tier one acoustic grands, and I can attest to the fact that this setup gives me the closest experience to playing those pianos as a digital setup possibly could.



This is a Kawai CP175 with AWA PRO Keyboard, Muse Receptor Module to run the "Akoustik Piano" VST sampled software through the MIDI system on the Kawai. The result is PHENOMENAL!!! Expect to spend $8000.00 to $9000.00 for this kind of a setup.

Voyager,

You are the only one I know of who has compared the GEM GRP-800 to the Yamaha CLP-270 (the RP-800 and the CLP-270 are my current short list items).

It's good to know that the keyboard on the RP/GRP is the same.

I'm curious (pertinent to this topic) how the sound of the RP-800 compared to the CLP-270 with iAFC? Did that stand out in any specific way or is that too subjective to comment on?

Any other comparisons between the two that you care to make would be appreciated.

Thanks.

I find the Kawai keys to be nice and feels great, but I won't say it feels the same as their RX series grand piano. All the RX-3s and RX-7s that I've tried out felt heavier than CP175 and CP155. Again, the actions on the grand piano can be regulated to be lighter, but even the Kawai Shegeru that I tried out with expert prep and voicing still felt heaver than CP175 and CP155.

My biggest complaint with Kawai action (which I think is one of the best digital actions) is that closer to fallboard, it is much harder to push the keys down than the real grand piano (or some other digital pianos for that matter). I think this is because Kawai uses real wood keys and action design, but the keys are about half the length of the real grand piano, which means you won't get nice even balance like a real grand piano does, becasue your lever is shorter.

Although Yamaha GH3 keys didn't feel quite as nice as Kawai, it does seem to have less problem with weight difference between fore and aft playing position. I don't know why, but it does.

(BTW, I own a Yamaha, so take this as my opinion)

Anyway, the whole point is that, every maker's digital action seems to be somewhat of a compromise. You might like one better than the other because you have preference for certain feel and is less concerned about the tradeoff that the manufacturer made.

This is, to some extent, a personal issue. I would suggest that you compare models in your price range of the 3 leading digital brands: Yamaha, Kawai, and Roland.

I have a Kawai and love it.

Great to see your setup CC2, I'm now more convinced that the Kawai has the best key action for the moment with the AWA Grand Pro keys.

And indeed the cheapest way to get the best digital piano, is to match a good keyboard with an external sound module. My setup is Korg digital piano with the Roland XR Fantom with coakley V sample piano (it's far better than SRX11) and I'm very satisfied with the setup too. But it's always nice to try out new things and the AWA Grand Pro keys and software samplers are next on my shopping list.

speedlever:

Sorry for not getting back to you right away. (Busy all day with vocal lessons). In response to your question:

Two points really:
1) I'm not sure if the iAFC function was turned on in the CLP270 when I tried it so I can't give you a good reply to that question, however I may be able to get some time today to go try that out specifically.

2) Sound is highly subjective (you're very right on that point) however a comment that you may find useful is this: The GEM products have a sound that is does an incredible job of sounding like a real acoustic piano (You really need to play an acoustic, a GEM and any other brand of digital, side by side in one sitting to really appreciate the quality of the GEM sound).

Can you get the opportunity to do a threeway test ?

Voyager

Hi Voyager,

I'll look forward to your assessment of the CLP-270 with iAFC. I'd almost bet that iAFC is on by default.

Regarding the 3-way test, I've had somewhat the same trouble with Yamaha as I've had with GEM. No local dealers carry the CLP-270/280. I have yet to lay my hands on one.

And to date, I have no idea where I can take a look at any of the GEM products. I realize that GEM is a small company and won't be found in every city, but I have not been able to get any dealer info yet to even know where to go to see the product. I put a request in (on the GEM website) about a week ago. Also, Dave M is trying to get some dealer info for me.

I'm somewhat troubled that dealer information seems to be a closely guarded secret. I would think that a small company would be pretty responsive when it comes to sales leads.

How did you find GEM? Did your local dealer just happen to carry them or were you looking for GEM?

Update to the dealer info: Dave provided my closest dealer in a pm yesterday.

Thanks, Dave!

Roland or GEM. The RD300SX and RD700SX are superb as is the Promega 2. The high-end Yamaha P-series are good, but not as good as Roland or GEM IMO.

Avoid Korg at all costs. Build quality is rubbish and their piano samples are horrible - tinny, unresponsive and coupled to clattery, plasticky key mechanisms.

I use an RD-300SX in all sorts of contexts (including solo piano gigs and as part of a 2-board rig with a JUNO-D in a band) and I am delighted with it. I'm used to playing my Schimmel acoustic, so I do have high standards.

Good luck making your choice!

Hi Dave,

Yes the Steinway & Fazioli samples are swaying me towards the GEM.

What about the action mechanisms for the RP, GRP, PRP? Do you know the differences?

Cheers

I don't doubt that it is phenomenal but for that money I would be looking at some top of the range uprights or baby grands.

What's the best setup for around £1000 or $1700?

Thanks.

I know the Korg is not well regarded but they have a new model called the SP-250.

Info

The samples don't sound bad.

It has a new action and a variable damping effect which seems to be similar to the GEM.

Pieter,

So you tried the MP8/4, ES4 and the sound was much worse than the PRP? I would have thought Kawai would be a close competitor. They also have used some kind of physical modelling and they have experience with acoustics.

I tried the RP800 the other day next to a Casio AP. Needless to say the the Casio seemed like a toy in comparison. I'm not sure how it would compare with the Kawais though. I really need to try.

I don't mind using headphones but you say the speakers are insubtantial. I think then, that the PRP-700 would be a better choice, saving a bit of money and weight. I could then add the amp/speaker of my choosing, maybe a Bosendorfer speaker.

Did you get any extras? The single pedal is weird b/c it's an on/off switch and that would make the Drake technology redundant to some extent.

The out of stock thing is a bummer. I think GEM could offer a discount for the ppl who are made to wait till July. Or perhaps include the triple pedal and stand. :p

Cheers

Mike

Yep, definitely the thing to do, much better than listening to too many personal opinions!

I like the fact that the sounds comes from the instrument itself, like amn acoustic, rather than separate speakers, so you can feel the music/vibrations through the keys. there's hardly any money and only 2lb in it.

pRP without the 3 pedal option is a waste of money imo!

£10 per week waiting!

Cheers

Pieter

"I'd almost bet that iAFC is on by default."

It might be on by default (not sure), but I think it has to be calibrated first. If not calibrated, true effect may not be clearly heard. (then again, no gaurantee if calibrated that effect may be clearly heard)

I just ordered a Kawai MP8. After looking at older grands, with their terribly uneven actions, I decided that the extremely precise action of a new digital is for me, at least until I can afford a Kawai 5-10 grand. (I had a Kawai KG-2D about 12 years ago, sold it for $5800, the same used piano goes for about $12500 now...). I chose the MP8 based on reviews mostly, and my appreciation of the Kawai action.

Interestingly, the manual says that the speakers automatically turn off when the headphones are plugged in. So you can only feel the vibrations when not listening through headphones??

Mike

Barbara C:
Congratulations on your choice. The MP8 is a great instrument.
Let us know how it goes for you.

Mikelangeli:
It's not for when listening through the headphones but when listening through external speakers! (I'm considering getting some yamaha stagepass 300 speakers, and a set of grado SR60 headphones)

I agree. I think based on the reviews it's one of the best keyboards ATM. The main thing that puts me off tho is the weight hence portability. So I am also looking at the MP4 or ES4.

The MP4 has more gadgets. The ES4 has speakers and "string resonance" modelling. Does anyone know if the latter makes a difference? The GEMS with the Drake engine have this feature too.

OK.

I was thinking about the Stagepas also. Seems like a nice little unit that you can use for other things as well.

My pRP800 has string resonance and it makes a world of difference to me. When looking for a digital piano, the first recommendations I got were The KawaiMP9000/9500, and the latest version the MP8. I was a bit gutted because they were totally out of reach for me. That's when I found out about the Gem pRP series for a third of the price. It doesn't have the Kawai's action though... Congrats Barbara with yours, coming from a Kawai acoustic I'd be keen to hear what you think of it, I doubt there's a better digital out there for you!

Absolutely. The "string resonance" and "damper effect" are major enhancements to my ear.

String resonance modeling gives your ep sound a rich compliment of harmonics. If you have this ability, try playing first with it switched on, then with it switched off. You'll notice the difference.

I just left this link on another post, so I'll include it here. The following site describes the theory behind these modeling techniques.

http://www.af.lu.se/~fogwall/piano.html

Kawai's harmonic imaging, as I understand it, is one of the simplified methods of doing "physical modeling". Physical modeling means to describe any part which can make sound or transmit vibration using hundreds of equations, instead of samples. Physical modeling is the only way to make convincing sounds for certain instruments like Japanese flute, for instance. It sounds indistinguishable from real when done in a very detailed way. You don't need samples, but unfortunately you need insane amounts of processing power. A piano is so complex that the problem can't be solved using physical modeling unless you simplify it a lot. Kawai's "harmonic imaging" they have in their MP8 and some other newer digital pianos is this kind of technology. Whether it is good or not good depends on how many simplifications were made in the equations. But I'm impressed that Kawai is going this direction.
Consider the alternative direction - massive sample collections. The Bosendorfer 290 sample set that uses over 1 Gigabyte of memory is praised by a lot of people as being the "ultimate" but I don't like it because it has too many abrupt transitions in the dynamics. My son has his piano set up this way (Roland RD700). If you play a note repeatedly, hitting the key a bit harder each time, you suddenly hear the Bosendorfer set move from one loudness set to another, and the difference is sometimes stark. But Kawai's method changes the balance of harmonics smoothly and continuously and you don't hear such artifacts. The down side of the method is that in a real piano there are dozens of harmonics that change as you modulate the key strike, and Kawai isn't going to model all of them, so that's the "simplification" part. It sounds good to my ear, so far, but I'll only know once I've lived with it for a while.
Reviewers of the MP8 have noted that they can hold down a key, hit and release a key in its harmonic series above it, and they can hear the first key, still held down, sounding in sympathetic resonance. That's just like a real piano. You can't get that kind of behavior out of sample collections no matter how many gigs they are.
Sorry for waxing technical, but I'm an electrical engineer so I'm easily impressed when I think a company has "done it the right way."

Well, that teaches me to read ALL the messages before posting. That article is great and everyone should read it instead of trying to decode my explanation above.

Barbara,
Where are you getting your information? I haven't seen any information from Kawai (including their website) that claims to use physical modeling. Rather, it seems to state that they use samples.

As for modeling technology, it's been used very successfully in the guitar world. But I have yet to hear a modeled piano that sounds and plays as well as a high quality sample.

It isn't hard to figure out some of Kawai's new methods by the comments of reviewers and owners. Clearly the dynamics and resonances are all computed instead of simply accessing sample tables. However I imagine Kawai still has a lot of samples in the MP8 especially for the non-piano instruments. But the best source of information is the website given in the previous message. Quoting the article (which is 2 years old - the MP8 is more advanced than the old Kawai pianos they are describing):

With all due respect to Niclas Fogwall, who I respect highly, I suspect that he is not referring to actual physical modeling, but rather being descriptive in his review.

Perhaps it's just me, but I don't find Kawai's pianos to be "clearly" modeled at all. I'm pretty sure they're based on sampling technology. Perhaps we could get someone from Kawai to weigh in on this.

Maybe you are thinking more of the sound source. There are pure physical models in which the original sound sources are sine wave oscillators. That's the purest kind of physical modelling. You have an oscillator for each harmonic which is present, and you modulate each one with respect to time. Any instrument imaginable can be modelled that way. Instead of that, what I believe Kawai did was to do a Fourier analysis of their EX piano and stored their samples as an array of coefficients instead of an array of time clips. In other words, the "samples" are in the frequency domain instead of the time domain. Mathematically the two methods are identical and result in the same sounds. But by storing the samples in the frequency domain, Kawai can make models which describe what happen to the coefficients under all the different conditions. A pure sample-based device wouldn't do anything but "look up" which sample to play, and perhaps set the amplitude for the sample. So there's not a black and white division between physical modeling and sampling. I'm sure the Kawai MP8 uses measurements from a real piano.

Isn't what you're describing just a sophisticated filter? Or don't I understand what you're saying (which is certainly possible -- I'm just a musician).

It's what's called a time-variant filter. Nowadays that's what is done in DSP's (digital signal processors). To do it to make a piano requires a lot of coefficients though. Then to do it with 196 voice polyphony, is just crazy. I can't visualize how they pull that off without an array of really powerful DSPs running in parallel. I've designed with DSP's before (implementing servo systems) but the task of synthesizing a full piano with that many voices boggles my mind.

Hi Barbara,

I appreciate the technical stuff as I did maths before so I get the gist of what you have said. As you are know about this, have you seen the videos on the GEM USA website. They are quite informative in terms of describing the modelling features on their Drake pianos. It seems they have 2 more "physical models" than Kawai has ie. Advanced Release and FADE (reproducing the harmonics for a given velocity).

Maybe Kawai have them too but they didn't bother to mention them for fear of confusing the non-technical customer.

This is nothing new, and is not "physical modeling". Just about every manufactuer of digital pianos uses this technology.

I guess I agree with you on that point, but a time-variant filter is just a generic term for anything that has a DSP in it. It doesn't have to mean that a product has physical modeling in it.

A sampled piano will use a time-domain time variant filter. It's a volume control. It senses which key you pressed, goes to a lookup table, and selects which sample to play. It filters it by setting the volume to match the key velocity. It might do the same to control sustain or attack-decay.

A piano which has pure physical modeling will use a frequency domain time variant filter. It has some equations which correspond to how strings work, how dampers work, how resonances happen, etc. It applies those equations based on which keys you press. That's the physical modeling part.

So a purely sampled piano is just a playback device. There probably aren't any of that sort anymore. The multi-gig computer sample library method would be my guess as the closest. The computing is mostly just to determine which sample to play, and at which volume.

A purely physical modeled piano is nothing but equations based on the behavior of a string in air which is struck by a blunt object. The sound is synthesized. There are no samples but a particular piano might have been used to tweak the constants for the equations. I doubt there is a piano which fully implements this sort of design since the calculations would be daunting.

What I think Kawai did was to start with a piano emulation. There would be equations but they aren't based on a physical object like a string, instead they would be rules for making a set of sounds which are a good match for their desired piano sound. Then, they added some real physical modeling on top of that to make its sound authentic. Since they started with an emulation they could save processing power to do the modeling of the physical effects. But the modeling would be limited to the things which modify or amplify the sound, like the interactions between strings, or the damper, etc.

But that's just my best guess. I suspect there are no pure sampled or pure modeled pianos anywhere for sale. Some university probably has a piano physical model programmed onto a big computer somewhere, but that wouldn't be a practical product. I would enjoy working on a project like that, but it's not my specialty. I wonder if there are some tests I can do on my piano to learn more about how they did it.

Barbara,
This is a very interesting dialogue to me. Thanks for sharing an engineer's perspective.

It seems to me that part of the confusion in the industry (and on this forum) stems from how "physical modeling" is defined. For example, you seem to be implying (please correct me if I'm misrepresenting you) that a TVF is a form of modeling. It seems that you're not alone in this claim as Fogwall's website and at least one manufacturer seems to agree with you. However, the manufacturer that I consult with wouldn't make that claim.

Your description above is consistent with what I view as physical modeling. It's used in guitar products by companies like Line 6, and in keyboards from Roland (VK series) and Yamaha (VL1, etc.).

Before I read your last post, I sent an email to Kawai US asking about the MP8. They were kind enough to respond very quickly. Here was the response:

He was obviously referring to the tone engine itself as not using physical modeling. His answer seems consistent with yours don't you think?

IMO, physical modeling holds a great deal of promise in the future. While sampling is in a sense, a dead technology, one shouldn't assume that a product that employs modeling technology will sound better than one that uses pure sampling. Implementation continues to be THE key factor.

Hope you stick around Barbara. Your input is valuable!!!

I would say so. Given what he said, it seems fairly obvious to me that the harmonic imaging is the emulation I spoke of.

When you hit a string, it vibrates and creates a sound which consists of fundamentals (a tone) and harmonics (higher pitched tones which are related to the fundamental). Generalizing, there will be one fundamental for each mode of vibration. A piano string has at least 2 modes of vibration, sideways and longways. Each mode might have 10-20 harmonics associated with it. There might be additional modes I am not aware of. Anyway, the problem is that the harmonics all have different amplitudes. Not only that, but they change according to time and how hard the string was struck. When Kawai talks about "harmonic imaging" they are confirming that they do all their calculations in the frequency domain - I.e. the amplitudes of the harmonics.

So take a simple case. If string 44 is hit it makes fundamental 400Hz with harmonics 2 thru 15. (The first harmonic is the fundamental). Lets say that if you hit the string soft, harmonic #15 does not appear. But if you hit the string a bit harder, harmonic 15 does appear. If you hit it very hard, harmonic 15 gets very loud. Meanwhile, harmonic 2 doesn't behave the same way. It gets louder as you hit the string harder, but not to the extent that H15 does. Kawai can write a complicated equation to describe how all 15 harmonics increase as you hit the string harder. They would need 2 of these equations per string, 176 in all. If I were doing it, the equations would actually be in the form of a piecewise linear lookup table. It would be a big table, because not only do the values change as a function of the hammer velocity, but also as a function of time. We're talking about thousands of coefficients. Once the whole system is working, the entire collection of harmonics can be figured out based on which string was struck, how hard, and when. Since the equations describe the behavior at EVERY point, the harmonics would smoothly change as you change the key press velocity.

On the other hand, a sampled system can't do that. The Bosendorfer 290 sample set (my son has it) has 16 sets of samples of the sound, one for each velocity range. A program receives the midi info and selects which sample to play. If you hit the key at different velocities you hear the harmonics change when you go from one sample set to another, but it is a sudden and totally unrealistic change. It sounds terrible to me. If the sample set had 256 levels, it might be ok, but it still would have other problems too.

So anyway, that's what I think "harmonic imaging" is, and why it works.