Yes, perhaps better on the Steinberg site... but we can help with some missing information concerning the S90 ES
In general the thousand dollar difference between the S90 ES and a Motif ES8 would account for many of the features (additional Knobs, Sequencer, Sampler, etc) missing from your S90 ES. Basically, the S90 ES was a cost down Motif ES, without the ISS (Integrated Sampling Sequencer).

Your question on using the General Remote Mode in your version of Cubase should be directed to your MySteinberg Account.
The S90 ES series (2004-2008) predates the big change over... that change over included the Yamaha AWM2 tone generator going from four Elements to eight Elements, and the Multi Part and Voice Editor being combined in unified Standalone/VST Editor... and the Studio Manager host application is no longer necessary. Cubase, after 2007, could act as host for the Yamaha's Synth Editors streamlining the whole setup.

The Remote DAW mode was completely redone as well. It was designed to work on ancient computers (the OS of that time). Even the Port assignments were different back then... In general, synthesizer hardware outlasts computer hardware by a huge factor... while your computer and its OS are obsoleted every year and a half (18 months), you keep your synth hardware for more than a decade... the fact that you still have an S90 ES is testament to just how long Synth hardware remains relevant. It's been fourteen years since we introduced the S90 ES... and ten since it was discontinued... your computer from fourteen years ago has been in a landfill site off the Jersey Turnpike for ten or twelve years by now.... And the fact that you are just now discovering this Remote DAW functionality speaks to the issue that at Yamaha we must be much much better at communicating that these features exist when they can be used properly.

Ten years ago I could have answered you (quickly) about your options concern the S90 ES and Remote mode, unfortunately, in the intervening decade, with all the computer OS changes and protocol changes for both Windows and Mac, I wouldn't even be able to tell you *if* the Editor runs on today's OS's. Cubase SX was out when the S90 ES first came out, and XP was the Windows OS... the computer world was all 32-bit back then... its all 64-bit now.

And because we highly (highly) doubt you are running Cubase SX, (you never did mention what version of Cubase you are using, but I bet it ain't SX!!!) You will need to check in with Steinberg about what still works with what, at some point software becomes *non-compliant*... computer-speak for "we obsoleted your software by changing your computer's system and hardware"...

I'd turn you over to our customer support folks but they maybe unable to test for you the S90 ES Multi Part Editor on any current computer either. Let us know, we'll try to help if we can

Thanks a bunch for such a quick reply! A few thoughts:

My first question was high level, and just out of curiosity -- if the S90ES requires enough of my attention to remote control my DAW instead of looking at my computer screen w/ mouse and keyboard, it seems like circular logic to remotely control the editor for the same keyboard -- because any changes to the multi can be done on the keyboard I'm already looking at. I was curious if there are other applications / performance uses I'm currently unaware of. My primary question is less about the Multi Part Editor and more about how to toggle track monitoring with the S90ES by any means, even outside of Cubase Remote Mode.

I use Cubase 7.5 (in fact, I use Cubase 7.5 32-bit in order to use Yamaha editors to perform deep voice editing on some of my PLGs via Studio Manager - exactly the thing that is no longer needed in a post-2007 world). I understand versions may lose compatibility with hardware, but the "Remote Control Devices" option in Cubase's Help menu brings up a pdf that is all about Mackie Control or HUI so I took this as gospel for my version too. In this document, most button names referenced are quite easily found on the S90ES screen in Remote mode, the exception being the Knobs (there is even a button called Knobs 1-4/5-8 which controls whether the faders [and knobs] apply to the first or second half of the bank of 8 DAW tracks, so I was looking for some gesture equivalent to "knob" pressing. I also must respond to the point that I'm only "just now discovering" the DAW remote functionality, I have always (well, since migrating to Cubase from Pro Tools) used the remote functionality in tandem with my computer, because in the past I only needed to record one part at a time for only a few bars. Now, my music is more live performance based so I'd love to have a streamlined way to get what I'm playing with my S90ES sequenced -- maybe the real solution is to upgrade to MOTIF ES, so I can keep my PLG cards and setup but gain the sequencer (and knobs, for that matter) I didn't miss until now.... but then I'll lose those beloved S700 samples! Internal conflict! If (and this is a BIG IF) I ended up doing this at some point in the future, it wouldn't be possible to sample the S700 samples out of the S90ES and add them to user sample memory on MOTIF ES, would it? I know the S700 samples were made available for the MOTIF XS series, and I understand why it'd be impossible to "convert" that to ES format (8 parts vs 4, among others). PLG board may be obsolete in the outside world, but I just refuse to let my PLGs get obsolete in my studio!

In any case, I have no problem asking a similar question on Cubase forum, but BadMister you've always had speedy and accurate solutions to my problems before so I figured I'd start here -- thanks again!

Upon doing further research and comparing the S90ES and Motif ES manuals side by side, I figured it out!

The Motif ES knobs are not also buttons (so there would still be no V-Pot toggle switch for track monitoring on/off) and in this case the manual describes this as knob switches, which the PRE1-4 buttons are assigned to emulate. The S90ES does not have the same PRE1-4 buttons however (its PRE buttons handle record enable toggling). However, cross referencing the S90ES manual looking for knob switches led me to the info that the VOLUME button switches the hardware faders to knobs! And instead of knob switches, pressing the ENTER button in remote mode will toggle monitoring for the selected track. Yayy!

There was some sleuthing involved, but I'm glad I figured this one out. I'm so relieved Yamaha was nice and smart enough to retain this much functionality/compatibility with Mackie Control specs in Remote mode despite removing the hardware knobs themselves! Amazing.

Thanks again Bad Mister - just making sure I had all my info when having this correspondence allowed me to find what I was looking for. My more academic/curiosity question about the original intent of the Multi Part Remote mode (i.e. only for multiple multi part yamaha synths?) still stands but is not pressing at all.