Hi Joseph, welcome to Yamaha Synth!

I have Cubase Elements 7 running on my IMac with MIDI Thru enabled.

I Add a MIDI Track to my Project with:

In = "All MIDI Inputs"

You need to define what "All MIDI Inputs" means to your system.
We ask because this is the first teachable moment in your post. YOU define what "All MIDI Inputs" means on the following screen in Cubase Elements 7:

Go to DEVICES > DEVICE SETUP... > MIDI > MIDI PORT SETUP... > In the very last column "In 'All MIDI Inputs'" what items are marked?

Only the PORTS that are legitimate controller Ports should be marked. This is for NOTE-ON data, Controller data, and Tempo... For example, you would mark "Motif XF6 Main" as this would allow you to use the keyboard and controllers of the Motif XF6 as an input device to your MIDI Tracks. Make sense? (Screen shot shows a Motif XF7, yours will identify your XF6)

You might mark "Motif XF6 MIDI IN" if you have a controller plugged into the 5-pin MIDI IN jack on the back of the Motif XF. Say you connect the MIDI OUT of the Tyros 3 to the MIDI IN jack of the Motif XF6. Then marking this PORT would include the Tyros3's keybed as a potential input device to a MIDI Track when you set the MIDI IN = ALL MIDI INPUTS. Marking these two would allow you to use either keyboard or both keyboards simultaneously as INPUT devices to your MIDI Track! Make sense?

You would never, never, never mark "Motif XF6 Remote" as this would cause front panel buttons on the Motif XF to trigger notes - Remote commands should be kept discreet.
DEVICES > DEVICE SETUP > REMOTE DEVICES > Set the "Motif XF6 Remote" for both INPUT and OUTPUT. This allows the DAW REMOTE mode to function properly.

You define what "ALL MIDI INPUTS" means by marking the INPUT device in the appropriate column. Only devices that you use to create NOTE-ON and other performance oriented movements (MW, PB Wheel, Foot pedals, Control Slider movements, etc). should be marked in the "In ALL MIDI Inputs" column.

With Motif Local Control = OFF the Motif does not sound anything

That is correct. LOCAL CONTROL literally means, "local"... the key press of the Motif XF travel directly/locally to the tone generator of the Motif XF when Local Control is ON. when you turn it OFF, it is completely normal for the sound to stop!!! That is correct! LOCAL OFF disconnects the XF keyboard from the XF tone generator! Absolutely!

With Motif Local Control = On the Motif sounds fine with no delay or echo.

Of course, by definition, Local Control ON means that when you press a key the tone generator makes a sound - no delay, no echo, just as if the computer were not in the circuit at all!!! The key press messages goes directly to the tone generator and the sound goes directly to the output (as if the computer where not even there). This is completely normal behavior.

If MIDI is Thru I expected the Motif to sound in both cases with the best result when Local Control is Off.

Your expectations are on the right track. The parameter setting in Cubase is MIDI THRU ACTIVE (don't forget the word ACTIVE)... When you shut LOCAL CONTROL OFF, it is imperative to complete the circuit. The KEY PRESS no longer triggers the Tone Generator directly, the message travels OUT via MIDI to the MIDI Track. There must be an *active* MIDI Track in Cubase to 'echo' or THRU (MIDI THRU ACTIVE) the data to a destination (tone engine). We have defined what ALL MIDI INPUTS are... now on the highlighted MIDI Track see the "MIDI OUT" assignment directly below. And the Channel number appears just below that.

You are sending the MIDI OUT to the Tyros3. The Tyros3 is defined by "Motif XF MIDI OUT"

Your FW MIDI Ports are as follows:
Motif XF6 MAIN = the Motif XF6 tone engine itself
Motif XF6 MIDI OUT = the Motif XF6's physical 5-pin MIDI OUT jack - to which you have the Tyros3 connected. MIDI OUT here, literally means the XF6's MIDI OUT jack
Motif XF6 REMOTE = the front panel mode DAW REMOTE - where all the front panel buttons, knobs, sliders are retasked with controlling Cubase.

If you want the Motif XF6 to sound, set Track Inspector's MIDI OUT = Motif XF6 MAIN
If you want the Tyros3 to sound, set the Track Inspector's MIDI OUT = Motif XF6 MIDI OUT

If you are using the "Motif XF Editor VST" - you will have an additional MIDI OUT selection to route signal INTO the Editor VST's MIDI In.

Hope that helps.

Thanks

My "ALL Midi Inputs" are as shown in your MIDI Port Setup display.

You said:

If you want the Motif XF6 to sound, set Track Inspector's MIDI OUT = Motif XF6 MAIN
If you want the Tyros3 to sound, set the Track Inspector's MIDI OUT = Motif XF6 MIDI OUT

So that is "either / or".

I wanted to sound both at the same time.. For example playing a Tyros Lead over a Performance backing.

You said:

If you want the Motif XF6 to sound, set Track Inspector's MIDI OUT = Motif XF6 MAIN
If you want the Tyros3 to sound, set the Track Inspector's MIDI OUT = Motif XF6 MIDI OUT

So that is "either / or".

I wanted to sound both at the same time.. For example playing a Tyros Lead over a Performance backing.

Each Track is used, typically, to transmit to a single device. You can activate as many tracks simultaneously as you desire. If you want to transmit simultaneously to both the Tyros 3 set the first MIDI Track's MIDI OUT = "Motif XF6 MIDI OUT", setup a second MIDI Track's MIDI OUT to transmit to "Motif XF Main" - highlight both tracks; you will transmit through each Track on whichever MIDI channel you set for that Track.

When selecting - the rules of your computer apply: "Shift + Click" selects all items in between. "Ctrl + Click" selects each item selected. etc., etc.

Ok, Thanks

Tried it. It works as you said.

Thanks again.