What's the difference between a Yamaha C3 versus S4? Is the S4 just a nice C3 the way a YUS1 is just a nice U1. According to something I read, the YUS1 shares all the same exact parts as the U1. Does the S4 have all the same parts as a C3? Similarly (C6 v. S6).

I think the S4 is a slightly different size and design than the C3. The S4 is built by hand much more slowly than the more mass-produced C3, in the same factory where the concert grands are made.

Unfortunately, I've never had the pleasure of playing one, but have tried and enjoyed an S6 and quite a few nine-footers.

C6 vs. S6 is an even more interesting question... same design a la the Shigeru Kawai vs. RX?

My wife played both when we bought the C3. No contest. The S is not just a nice C. My wife felt it was comparable in quality to the new Steinway NY she played. No one would ever say that about a C. The Steinway and the S were well out of our price range.

IMO, the S belongs in Fine's Group 2. There's a thread on this -- in which Fine admitted that it's somewhere between Group 2 and Group 3.

However, if you can afford an S4, then there are a lot of other excellent pianos that you can buy. You should try as many as you can. To name a few: Estonia, Shigeru Kawai, M&H, Grotrian. All good, but all very different, and some a much better value than the S, if you like them of course. I'd also compare Kawai RX to the C. Often cheaper with better action and sound IMO.

If we're discussing new:

C3 - mass produced 6'1" 704lbs good reputation, very approx price UK£16000 = US$25000

S4BB - hand built 6'3" 737lbs tuning stability questions?, very approx price UK£27000 = US$43000.

C6 - mass produced 6'11" 891lbs good reputation, UK£22000 = US$35200

S6 - hand built 6'11" 842lbs good reputation, UK£30000 = US$48000

Handbuilt Yamahas have a superior soundboard, better strings and hammer felt, although IMO (in the case of Yamaha pianos), a longer C series sounds better overall than a shorter S series.

Conclusion - don't buy an S4.

Very interesting. So by your judgement, would you take a C5 over an S4?

It has to be said, I've been entirely underwhelmed by the S series. I played a few in London last summer in the main Yamaha showroom there, and they really were not particularly impressive. The actions we good and controlable, but the sound was (strange to say...) refined to the point of entirely uninteresting. Equally, some of the instruments were very badly set up. On one, I played it and thought that the sound was quite stifled, and suggested that it felt and sounded like the strike point was not quite right - the tech that was with me had a quick look and sure enought I was spot on (which does not often happen!).

I have to say that the C6 and C7 I played at Chris Venables (and I'm just sorry that we did not buy from there in the end - we found a stunning nearly new Schimmel that pipped everything else to the post) were far more enjoyable instruments, with a good rounded sound, and as much complexity of sound as Yamaha's manage, to really give you a sound you can craft. I'd much more happily live with a well set up and maintained C series, than either of the S series that I just don't find worth it.

I'm not entirely sure about the Shigeru Kawai lineup either in terms of what one ultimately gains over the RX series...

I've heard others rave about the S series, particularly the S6 - but of the four I've played I've been really disappointed. I often hear it said that they are very like a Steinway B (I've only ever played Hamburg, but have probably played hundreds of them) and I find that the Steinway B is simply an entire universe away from the S6 in every way... I fear that the S thing might be quite a lot of hype...

Yes, for the reasons previously given, but also if I were a customer I would pay a little extra money over the C5 and get a lot more piano with the 6'11" C6. We hardly ever sell a C5. Not enough of an improvement over the C3 for the price premium, whereas the premium is justifiable from C5 to C6.

Sorry, forgot to answer your original query regarding the U1 and YUS1 having the same parts. No they have different strings , different hammer felts and a different case style, but use the same frame and soundboard. Ditto for the U3 and YUS3.