? Which product are we talking about?

If you are talking about a synthesizer with XA CONTROL (you mention "legato elements" so we assume this is the case, Portamento has several modes as well and can indeed affect the AEG. Portamento can be applied "fulltime" or in the case of a MONO Voice it can be applied only when you play legato

If you are having a specific problem please provide details - we can guess at what you are seeing/hearing or we can attempt to help you specifically demystify what you are seeing/hearing (if we can).

it's funny that when I own something and I want to ask a question, I assume you also have it! My bad, well I'm talking about the MOX. I have two elements set to legato (XA control menu under OSC section). The general params are:
Mono/Poly: mono
Key Assign: single
portamento params are:
Switch: ON
Time Mode: rate2
Time: any value less than 30
Legato Slope: 7
Mode: fingered

I want to the elements to have attacks-based velocity. This works when the Portamento switch is OFF but as soon as I set it to ON AEG set up is overridden (ignored). If it's not possible, what are my options then? (BTW Phil I'm still waiting for the news about the legato Strings).

In order for XA CONTROL to work as intended, the "legato" Element should be set to a Waveform that does not have a pre-recorded attack. In the Wave ROM are specific Waveforms that are OFFSET so that the sound begins post the normal attack portion of the sound, this avoids any issues as you are describing.

Remember these are sampled instruments, which when recorded typically include the musician's natural attack. In order to record a flute, for example, every note played by the flute player is attacked and held. In order to create a legato gesture when performing with this data Yamaha includes a flute Waveform sans the attack, it actually begins some time after the initial recorded attack. These OFFSET waveforms are to be used in the legato XA CONTROL gesture - assign an offset Waveform in the legato Element. If you use a Waveform where the sample includes the musician's attack, it will play like every other sampled based synth... Your phrases will be attack-attack-attack every note in the phrase will be as if the flute player took a breath.

If, however, you use an offset Waveform you can attack only when you lift your finger and attack the key, but if you trigger another note without lifting your finger, the MOX will "know" you want to execute a legato gesture and will "knit" the offset Waveform into your performance. This allows for a more natural phrasing from samples.

Be sure your legato articulation Elements have "Of" in their name to ensure they are the intended 'offset' attack waveforms.

If you are attempting to use this Portamento to match what was played in that video, again, I'm not at all sure that was involved. Just saying...

Thanks Phil. We are both on the same page. I have my elements setup exactly the way you described. My problem is not the samples themselves but the articulation I want to achieve.

My purpose for the following paragraph is just to explain what I want to achieve and by no means I want to teach anything. You're a great musician far beyond my knowledge so my apologies upfront don't want to give a wrong impression at all. It's just I can't think of a better way to explain some of the details by a simple example on the real instrument.

As you know in violin, the player can introduce complicated articulation using both hands. One with the fingers and the other with the bow and they are both independent. To accentuate the notes, player can push the bow softer or harder towards the strings. Now imagine when the player wants to coordinate this technique with a legato part. The player can accentuate the beginning of every slur using the bow. At the same time, the player also has control over the length of the slurs. So what I want to achieve is be able to simulate the accentuated notes by velocity and AEG, meanwhile, portamento time specifies the transition time between the notes.

No when I don't have Portamento ON, it works as expected but for notes that are far from each other I want to have some portamento involved. This, ignores the AEG... How can I fix it?

Okay, this helps a bunch. I'm not sure you can fix this in the keyboard alone, I'll have to research it. The Portamento parameters are all about adjusting the distance and speed of change. But since I don't personally use this feature, I don't have any quick tips. I'll have to research it.

The keyboard as a controller is ideal for triggering and controlling percussion instruments (keyboards are, in fact, percussion instruments); to emulate any other instrument type you have to get creative.

Velocity can be asked to do too many things, what you need is a way to map Velocity to a cc (005) then you might be able to control how much Portamento Time is applied as you play but then you will need another controller to be in charge of how loud you are ...this could be done.

An input transformer would do the trick. Are you a Cubase user?

I do have another controller not sure if it meets the requirements? In terms of the DAW, I have the Cubase bundled with MOX (which is AI/LE version) and I recently got logic and mainstage.

I do appreciate if you explain the rest of the what you had in mind Phil.