Thanks Bill and athomik,
I appreciate your responses. The advice about not touching keys while it is booting up is good to know. Also glad, Bill, that you like the samples so well.
My question is not about the mechanical action of the sustain pedal. Rather, it is about the sound of the samples activated by the sustain (and/or by holding a note down). Let me explain.
One way to think about each digital sample for each note is to consider that the sound comes from a combination of two sounds. First, there is the primary sound from the note itself (its own strings). Second, there is the secondary sound from all the other sampled notes echoing when sustain is engaged. In real life, the primary note sound diminishes a bit more quickly than the secondary echoes, which fade out last.
Now, on the lower notes of my new USG1 (e.g., C below middle C), the piano sample functions similarly to acoustic, albeit a bit shorter. That is, the primary note sound lasts for about 3 seconds, and the sustained sound continues on for quite a while thereafter (~30 sec, compared to ~45 seconds for the acoustic sound of the same note).
On higher notes, however, this changes (e.g., C above middle C). In this upper register, however, the primary sound of the note seems to die off prematurely (only about 1.5 seconds) as though dampened, leaving only the sample of the sustained echo from all the other strings. The total sample lasts about 15 seconds (compared to 30 seconds for the acoustic sound of the same sustained note).
In the even higher notes (e.g., two octaves higher), the entire sample (while the sustain pedal is pressed) only lasts for about 4 seconds and seems even more strongly dampened, almost clipping off. In fact, these notes sustain longer when the note is simply held down with no sustain pedal.
Finally, there is one other unusual sound. The A above middle C has a pronounced vibrato (almost wa-wa) after a few seconds of sustain.
My concern (thank for your patience reading this!) is that I wonder if there is something defective with how my piano is playing the samples. I find it hard to believe that Yamaha would not have invested a tiny bit more time into making these notes sustain more realistically, particularly when the other samples (e.g., vibraphone, strings, etc.) do not seem to die off anywhere near as quickly.
The obvious easiest way for me to test this would be to play another new UGS1, but they seem to always be special order items, never sitting in a show room. Hence, I was hoping that the sample might be the same in a disklavier (which often DO sit in show rooms). My final hope is that someone truly familiar with the UGS1 samples could tell me if I am describing the samples as they exist in ALL UGS1 pianos, or if there might be something wrong with mine.
Keep in mind that a casual listener would likely not detect any of these things. However, my personal piano technician agreed with my assessment. He thinks that this just might be the nature of the samples Yamaha uses, but that surprises me given their outstanding reputation.
Thanks for whatever insights you (or anyone!) might have.