Im S90XS-Forum hat sich jemand von Yamaha hierzu gemeldet.
Kurzzusammenfassung der Antwort: Diese Funktion ist esoterisch und kommt nicht. Für Yamaha ist es unüblich und esoterisch eine hohe Fläche mit der linken Hand zu spielen.
Ich finde das Verhalten von Yamaha unglaublich und werde dieses Verhalten in bei zukünftigen Käufern aber auch bei Empfehlungen berücksichtigen!
Hier die Antwort im Wortlaut:
The keyboard is programmable and provides ways to do most things (within reason). When I say 'within reason', I am referring to those things that would be done most commonly are going to be easiest to do, those things that are esoteric or unusual may require that you roll your sleeves up and to do some programming.
Your request (believe it or not) falls into the slightly esoteric or unusual category. Bass sounds are programmed low enough on the keyboard to be accessed by the left hand and lead sounds are programmed to be accessible by the right hand. This is normal and usual. When you need a sound to be four octaves out of its normal range, that falls into the realm of esoteric and/or unusual. Now, respectfully, you may not agree, and I understand this but this is how the instrument is designed. It is not that you cannot do what you ask, it is just not one of the those things that is easily accessible. I hope that is clear.
MIDI provides a 10 and a half octave range (C-2 through G8), that's 128 notes, even though the instrument with largest range is the piano (88 notes, A-1 through C7. Most musical instruments fall somewhat (far) short of that range. Let's use a flute for example, its range extends from middle "C" (C3 on a Yamaha keyboard) three octaves to C6.
Why you would need to move this 4 octaves lower (that is, so that the lowest note would wind up on C-1) has to fall into the category of esoteric and unusual, but not only that, what happens to the upper end of this Voice. With the range of the flute on the keys from C-1 through C2, what now happens to the keys C#2 through the top of the keyboard? (They become unplayable high and eventually stop sounding.) And this is why I say this is not usual...
We understand that you probably have a 'good reason' for your request, but you have to understand why it qualifies as an unusual request. And that because it is not something that most people would require often, it requires some programming. But the bottom-line is, in fact, it can be done!.
It is not impossible, but because it is unusual you will have to go the extra length to accomplish it. There is nothing wrong with your request, other than you think it is something that is "required" from a keyboard (price not withstanding). And I guess somewhat the engineers agree with you - because they do allow the keyboard to be programmed to do it. Just not how you expect it to be done on a keyboard/synth in this price class

-) sorry.
If you require a Voice to be four octaves out of its normal range, you will need to program the Voice (at the Voice Element level) to do so... then place that VOICE in your PERFORMANCE. And as you will find out when you do this, it is really an unplayable Voice outside of the esoteric and unusual application.
What you need to do (although, I'm probably wasting my time writing it out as you have probably already decided it is even more long-winded than going to MASTER mode) involves tuning the individual ELEMENTS of the Voice, storing a new USER VOICE, then using that newly edited Voice in your Performance.
Each Element (at the Voice Element editing level) can be Coarse Tuned +/-48 semitones from its normal range. This will allow you to create a flute, for example that plays from C-1 through C2 or a bass guitar that starts at E3 and extends up. With the S90XS/S70XS you will need to use the Editor to do this type of Element editing. For those willing to do so, the reward is that you can accomplish the goal, however, if it is too much trouble or too long-winded, then you can wait for an operating system update (that, frankly, may never happen - although it does not hurt to ask, and trust me, I will ask). Coarse Tuning each Element will create a VOICE that can then be positioned on the keyboard as you desire.
Unfortunately, there is not a quicker way to accomplish this, but there it is ...