Has to be done with fmx for that glide type. May already be a present.

BTW: if these are free packs (public domain or legitimately provided free of charge from original sources) then a link would help. I wasn't able to find those sets. I do have an EX5. If they are similar to the video - then chances are they are virtual analog "AN" engine of EX5 which has no one-to-one equivalent on MODX. Although the sine-ish nature of the sound in the video lends itself to leveraging FM and perhaps applying filters/effects to approach AN.

Hey Jason,
Thank you for your response!

what do you mean by done with f-mx? I'm newbie at the MODX and Yamaha in general (I'm coming from Nord world)
I'll appreciate if you can explain me to details please.

And sure, these are FREE packs from Jamal's website (this is the link to download).
I uploaded here the ZIP file to these packs so you can check them.

Do you have a clue how I can create this sound exactly on my MODX?

The EX5 has a bunch of methods to produce sounds ("sound engines" ). One is sample based (AWM) and matches pretty much what MODX has in AWM2. The rest of the engines are not inside MODX at all. There's AN, VL, FDSP. A bag of tricks that MODX and really no other keyboard has has in a "Swiss Army" knife kind of way. The sounds you want are from the AN engine - a digitally generated analog modeler. MODX doesn't have this - but the property of the "glide" can be replicated with FM-X. FM-X is using frequency modulation, an additive synthesis technique that was popularized in the DX7 - Yamaha's most successful keyboard (IMO - and possibly factually by sales volume).

I don't know how exactly to describe how to do it - I'd have to play with it for a little while and try first to find a built-in preset that already does this. I'd search by filtering only the FM-X performances and also look at the synth lead category. Having auditioned those - I may find something close enough. If not, I'd start making my own FM-X Performance and really focus most on getting the portamento timing correct so the glide acts the same - then work on getting the sound close enough - probably just sticking with a clean sine waveform.