Kawai VPC1 vs CA701 vs Casio GP310/GP510

After reading a bit it seems that the Kawai (GF series) key sticks are a few cm shorter than the Casio's, but the Kawai's pivot points are a few cm longer than the Casio's. Maybe a counterweight trick? That likely explains the difference I was feeling. I had read the Casio had longer keys so assumed it had a longer pivot point too, so was surprised by how it felt. However it was very responsive, with good repetition.

Well on acoustic grands they have actual escapement (not just escapement-feel), so as you release a key the weight of the hammer isn't added to the key's weight. That results in a light/responsive feel (perhaps with other complex mechanics helping, I'm no technician). The sluggishness in most digital keyboards from my experience is due to no actual escapement, so a slower return. That combined with a heavier action (like my old MP8) results in a really sluggish feel. Maybe some makers use tricks with springs and such to minimize this, but every digital I've played on feels sluggish compared to a modern 9 foot Steinway, Kawai, Yamaha, etc. Again, the heavier action digitals just seem to make the sluggishness more noticeable.

I find this sluggishness annoying, but it's something you can get used to if it's not horrible and if the key returns fairly quickly. But a big difference between key weight at the front of the key vs. the back of the key -- that's something that's always going to hinder you, and you really don't want to get used to it.

For the record, I'm a classical pianist, not a technician, and my knowledge of digital keyboards is fairly limited. I had an old flagship Roland many years back, and it was terribly sluggish (worse than my old MP8). I'm sure they've improved, but have only tried some of their current mid-tier actions.

Pianistically wrote:

I completely agree with your analysis . In my opinion , return speed is even more important than pivot length . As a matter of fact , shorter pivot length makes playing close to the fall board more difficult but still possible but slow return speed is just a show stopper and is a major road block blocker for fast trills and repetition speed . VPC1, Kawai GF actions have slow return , they are excellent keyboards for dynamics control but are just to slow . What I find irritating is that some cheap entry level keyboards beat these relatively expensive keyboards for virtuosic passages.

Funny, I actually have almost the opposite opinion! Well, not really...

I find a short pivot point and extremely sluggish key return speed to both be show stoppers. High-end keyboards have improved over the years in both areas and in my opinion the (far from perfect) GFIII action is decent in both. However, the "short" pivot point of the GFIII action bothers me more than the key return speed/feel. I don't actually find it problematic at all in playing fast trills or extremely fast/delicate figures. It's actually a bit more responsive than the VPC1, which has a much shorter pivot point. Do you have to get used to it? Yes, definitely. It doesn't feel great, but it's not that bad IMHO and gets the job done. So I wouldn't personally call the sluggishness/key return weight of the GFIII action a show stopper.

The "long" (but not long enough!) pivot point of the GFIII action on the other hand makes it basically impossible to play perfectly smooth phrases. Subtle cresc. and dim. will be slightly mangled when the thumb and pinky are towards the center of the keys (pressing more easily, thus louder) and the longer fingers are towards the back of the keys (pressing with more difficulty, thus quieter). For really fast passages at the fallboard it can also be very problematic. Again, on the GFIII action it's certainly not terrible and I'm sure most people wouldn't even notice it. But I'd say it borders on being a show stopper for a lot of difficult music and it's definitely a show stopper on the GP310/510 and most other keyboards. And again, it's a shame because those Casio/Bechstein keyboards are even more responsive and feel very nice (not perfect though).

If you get used to playing a somewhat sluggish action, then move to a nice grand piano, you'll have no issues adapting. It will feel great. If you somehow managed the perhaps impossible feat of fully adapting to playing smooth phrases towards the back of the keys with a short pivot point, then moving to a nice grand piano would be problematic as you would instinctively play with more force towards the fallboard with fingers 2, 3, and 4. Again, assuming adapting were possible. I think in reality your phrasing and technique would just be a bit compromised while playing your keyboard, but on a good piano things would suddenly work better and feel much nicer.

I should note, these thoughts are only based on my own personal observations playing pianos and keyboards. My students (those who aren't beginners) all practice primarily on pianos.

...or try a trill with fingers 4 and 5 near the felt on a keyboard with a short pivot point and somewhat heavy action...not fun. Luckily not much practical need to do that...but there's probably some Bach fugue where you might want to...

Pianistically wrote:

I have owned my MP11 for more than 10 years , I had a VPC1 before and both are limited when it comes to repetition speed with the black notes. The relatively long pivot length of the GF action ~23.5 mm makes playing close to the fall board easy but I find the return of the key quite sluggish. Exceeding a repetition of  10 notes per second with alternate fingers with one hand is more than challenging on the black notes with high risk of ghosts notes as its difficult to produce a sound just above the middle sensor , your fingers just need to be slightly above. The VPC1 which I sold a few years back has a quite short pivot length ( less than 20 cm) plays well but  main issue is key agility . The main issue of these wood actions is that they mimic acoustic piano key design , including the let off feeling but the big difference and what makes a huge difference in a grand action is the double escapement entire...

Yes I've never liked any keyboard for fast single-key repetition. The cheaper springy keys are fast, but don't have the momentum/kinetic mass of a piano key, so they feel and behave completely differently (in a really bad way!). The decent keyboard keys that see-saw like piano keys are too sluggish and heavy on the key return (as you point out). I'm sure it would be complex and expensive to replicate a true escapement, let alone Steinway's double-escapement or the equivalent of other piano makers, plus I'm sure it would mean more to maintain...which most people wouldn't want.

As it stands I find the VPC1 fairly bad when it comes to single note repetition, but I found the GFIII in the CA701 to be a decent improvement, and the GP510 to be a tiny bit better still. Those last two still don't feel nearly as good or as nimble as a nice grand piano, but grands vary a lot in the "nimble" category when it comes to single note repetition...many are really not great at all! I find that it takes a slight technique modification (which I developed on my old MP8, which had really bad repetition!), and it's certainly more laborious, but I could produce a pretty adequate single note repetition on both the CA701 and GP510. So to me they get the job done, but that much heavier weight at the felt of the GP510 was a real deal breaker.