Sorry, for the delay. I wrote out a whole response for you and then closed the browser without clicking REPLY (my bad). There are a couple of things we can get you straightened out on and hopefully this will start to bring things together for you.

Basically, with the Motif's mLAN Monitor set to "with PC", I get no sound at all. With mLAN Monitor set to either "stand alone" or "with PC (Direct Monitor), I get my Concert Grand voice with the sustain stuck on and half the notes I play dropped.

The mLAN MONITOR SETUP has three different settings and each has reason to exist. It is not at all unusual to get "no sound at all" when you select the "with PC" option. This basically changes the routing so that audio no longer goes directly from your XS to the Main L/R outputs. The "with PC" literally means, your audio out will go to the Personal Computer prior to it returning to the XS and the Main L/R outputs.

So "with PC" will require that you meet the setup criteria within your DAW software to route the audio back to the Motif XS. Unless you complete that circuit, no audio. So don't panic just yet. "with PC" disconnects the DIRECT audio path between the XS tone engine and the analog outputs!

Typically, when you play your XS keys, the sound goes directly to the outputs (simple, straight ahead). When you opt to use the "with PC" you are wishing to hear the audio generated post it traversing the software. Why? because you are wishing to hear it post (or after) it has been processed in your DAW software (this is the so-called "virtual audio" routing scenario. So the "With PC" disconnects the audio stream that normally has the XS sending audio directly to the analog audio outputs, and ensures that the initial audio stream will travel via FireWire connection to the computer and into the software... where you then make settings to process that signal and return it finally to the XS and the main outputs which feed your monitor speakers.

"Stand alone" is self-explanatory. This is when you are using the Motif XS without a computer connection at all. Like when gigging or just playing it.

"with PC(Direct Monitor)" is the third option and to understand this, remember the XS is your audio interface. We talked about the audio going direct to the outputs, and we talked about defeating that and sending the audio to the computer first, for processing then back out. This combines the standalone (direct to the outputs) and the Routing that includes the "with" computer routing. Why would you need this? Because in a situation where you are playing back audio from the computer while you are adding NEW audio you need this dual option. The signal that you are playing 'live' on the XS travels direct to the outputs and it travels to the computer BUT, significantly you don't monitor the signal going to the computer during recording (you want to hear yourself DIRECT). You do want to play along with audio coming from the computer.

This is useful for overdubbing. You need to hear audio already on the computer, but you also need to hear yourself playing. Any audio that must travel to the computer, be processed and then sent to the outputs is called the LATENT signal (yes, as in "latency") and will be slightly behind the DIRECT signal. IF you have both streams audible, you will hear DOUBLING. The DIRECT signal arrives first (obviously) and several milliseconds later you hear the signal that traveled 'to' the computer, got processed and sent back. So when you select "with PC(Direct Monitoring)" you want to make sure you defeat (in your DAW) the latent signal. Hearing yourself direct means you can play "with feeling". So this setting allows both streams, but let's you select which *one* you will monitor. Sophisticated "delay compensation" routines in Cubase ensure your audio is positioned properly.

Again, it is all about signal flow and routing scenarios. This is the audio equivalent of LOCAL CONTROL. (if you don't understand that reference, let us know) it is all about where the signal is allowed to flow. And as with any electrical signal flow, you must complete the circuit for the light bulb to come on. So in the case of audio routing, you want to know just how the audio you are playing gets to where it is going.

"With PC" assumes that you are setting up the Motif XS with VSTi routing (Virtual Studio Technology instrument) - a standard protocol invented/innovated by the folks at Steinberg - can be viewed as a signal routing protocol that allows external audio devices (as well as those on the computer) to be a part of the recording environment. If you select 'with PC' you want to have a situation where the MIDI Track is set to receive data (MIDI IN) from your Motif XS on PORT 1, and that same MIDI Track is set to transmit data (MIDI OUT) to the "Motif XS VST-MIDI In"

Yes there is going to be a difference between the "Motif XS Main" as a MIDI IN and the "Motif XS VST-MIDI In". Please recognize they are not the same thing. If you select the "Motif XS VST MIDI IN" while "with PC" is selected, then (and only then) will audio arrive at the VST INSTRUMENT audio lane found in the Motif XS VST Folder.

Here are some basic things to check inside your Motif XS:

When you are using the Motif XS with the Yamaha Steinberg FW driver (YSFW) you need to verify the following AUDIO and MIDI settings in your Motif XS:

AUDIO SETUP
Press [UTILITY]
Press [F1] GENERAL
Press [SF4] AUTO LOAD
Ensure that the IEEE1394 Driver = FW

If not set to "FW", change the setting, then press [STORE] to write this preference to your Flash ROM
You will need to reboot the Motif XS for this setting to take place. Once stored, however, your unit will have this setting as part of your system settings from then on.
If you do not see an option for "FW" then you need to do some updating. You are using the Yamaha Steinberg FW Driver so this needs to be set to FW in order to work. If the "FW" option does not appear - let us know.

MIDI SETUP
Next, you want to make sure that the MIDI communication is set to mLAN:
Press [UTILITY]
Press [F5] CONTROL
Press [SF2] MIDI
Ensure that the MIDI IN/OUT = mLAN
Press [STORE] to write this preference to your Flash ROM.

All MIDI tracks have come up with their Input and Output Routing set to "MOTIF XS8 Main". Checking Devices > VST Connections shows both input and output busses "MOTF XS8 Main" are connected to device "Yamaha Steinberg FW ASIO", device ports "MOTIF XS8 Main L and R".

Whether or not you are should see VST CONNECTION > INPUTS will depend on whether or not you are going to be using the "Motif XS Editor VST"

In other words, if you are using the Motif XS Editor VST, then your audio routing will take place inside the EDITOR itself, (not on the VST CONNECTIONS > INPUT tab). You can connect the Motif XS two different ways but not both, it is EITHER / OR.

Either you are using the EDITOR VST which has the audio connection inside the Editor - - OR - - you can manually setup the VST CONNECTiONS > INPUT tab
But never both!!! It doesn't allow you. I know this sounds strange - but really is not. If it were a input jack on a mixer you would see that the synth is already connected - and once you plug the synthesizer into the audio input, that input is occupied. So if you connect the synth via the EDITOR VST the input jacks are occupied (you would see this if it was real world analog connection)... once connected via the EDITOR VST, the option to select it under the VST CONNECTIONS > INPUT screen disappears.

So are you planning on using the Editor VST?

Device Setup > VST Audio System > Yamaha Steinberg FW ASIO shows:
In Ports = MOTIF XS8 Main L, MOTIF XS8 Main R, MOTIF XS8 1 thru 14 - all "Active"
Out Ports = MOTIF XS8 Main L, MOTIF XS8 Main R, MOTIF XS8 FW L, MOTIF XS8 FW R, MOTIF XS8 Asgn L, MOTIF XS8 Asgn R - all "Active"
MIDI PORT SETUP shows MIDI In = MOTIF XS8 Main and Remote both "Active", and same for MIDI Out.

All active, yikes, okay but the ACTIVE / INACTIVE is just a status report. You probably do not need to ACTIVATE everything all at once. In fact, that's wrong.

Depending on what you are doing the Active/Inactive column is there for troubleshooting - only when you have made a connection to an INPUT or an OUTPUT do you see the "active" status. Yes you need the IN PORTS (Main L and Main R) active and yes, you need the OUT PORTS (Main L and Main R) active.

You only need the FW L and FW R options active when you are planning to route signal back to the Motif mixer or sampler.
You only need the Asgn L and Asgn R option active when you are planning on feeding a headphone amp or second pair of monitor speakers.

And as far as MIDI PORT SETUP - this is critical ... Only devices that are going to contribute data to your DAW MIDI Tracks need to be marked in the IN ALL INPUTS column. Do not mark REMOTE, that would cause chaos and front panel buttons will start triggering musical notes, and keys will start opening DAW windows, and madness quickly follows 😉

so for example, the Motif XS Main - is your primary INPUT device - it should have a check mark in the IN ALL INPUTS column
If you have a secondary MIDI controller connected to the 5-pin MIDI IN jack of the Motif XS then you would mark the MOTIF XS MIDI IN Port, otherwise, just the Motif XS Main needs to be marked.

No worries - My turn to reply slowly - by coincidence, I'm on the road again, and so will go through this in detail when I get back in a few days.

But thanks heaps for the detailed info.

Wow - FINALLY able to get back to this. Sorry for the late late reply - life took a left turn in September.

Anyway - in the meantime I have re-read and pondered your last post and, miracles, have the Motif and Cubase talking. Both with and without the Motif XS Editor VST. Thank you for the explanations. OK, the VST editor makes it really easy - add it to the VST Intrument rack, and it does all the setup automatically, pretty much.

BUT - probably a character flaw - I need to delve into the workings of this and understand exactly what's going on wit respecyt to signal flow, these Utility switches, etc.. So, I've fiddled and reasoned and will inflict a new thread more generally on Motif-Cubase Routing on this forum.

Thanks.