Can I control an arpeggio playing with key velocity on MX?

No, not at all. Velocity Mode is fixed to play the originally programmed velocity for the Arp Phrase (as it was originally created).

Thanks for the question... it gives us an opportunity to talk about the synth lineup. Currently, the MONTAGE, MODX and MX makeup the full-sized keyboard synthesizers. The MOXF8 can also still be found... (as can the mini-key refaceYC/CP/CS/DX)

Many times people are unclear on the similarities and differences in the products. And it takes awhile to clearly understand how, in this case, these different models share certain features and where the differences exist. In general, among the full sized key synths — the MX being the entry level model has a “best of...” concept... borrowing the ‘best of’ library of sounds culled from the Motif-series synth sounds. And while it features arpeggiators (2x999 ‘chord intelligent’ Types), and rhythm patterns (208 drum grooves), you do not have the same capability of creating your own, nor do you have the advanced functions such as realtime adjustment to Velocity Mode input, Timing offsets, etc (called Arp Play FX in the more advanced models).

It should come as a surprise to no one that as you move up in price in any product listing, the more elegant and often the more programmable the instrument becomes. The MX does not feature a recording sequencer, nor does it include *deep editing* via the front panel. Third party Editors (John Melas MX Tools) give access to many of the Voice Editing functions that exist under the surface. Combine the less expensive hardware with a computer and you have added some of the features that allow the MX to be affordable. This allows both those not interested in deep editing and those curious to get started in deeper editing a reasonable solution.

It’s not a bad strategy to offer as many sonic features as possible from the higher end models (no one wants to skimp on the SOUND)... but recording, and editing which many already do with DAWs can work for a large group of potential customers who may already have an iPad or laptop computer.

Consider carefully feature sets when seeking to purchase a hardware synth. In the MX, you have a 3 model series with plenty of pedigree in its sound library... it has 49, 61 synth action and a full 88 key weighted action versions... that deliver 128 note polyphony at basically under a thousand dollars. When you move into the next price-point range where the MOXF and now the MODX live, you add the ability to create your own... you graduate to many on-board features and functions that allow more control over things, including the arpeggiators... the MOXF features 4 programmable Arpeggiators (7,981 types), the new MODX features 8 Arpeggiators (10,231 types).
MOXF you can make and store 256 of your own User Arps on board.
MODX you can not only make your own Arp phrases you can store 2048 of your own on board and create 2048 Motion Sequences (a Motion Sequence is an Arp made for ‘automating’ parameter control.

Here in the next thousand $$ price range (MOXF/MODX), you’ll find features like Velocity Mode, Velocity Zone Arpeggios, etc. Velocity mode allows you to adjust the Arp phrase with key-on velocity (provided the sound is velocity sensitive). The velocity of the controlling Key-on event can either be heeded or ignored as a programmable parameter.

You did not include the name of the Bass program - be sure it is a velocity responsive sound. (many analog synth emulations are purposefully set to fixed velocity, particularly if emulating a Moog Synth Bass or an Arp Odyssey Synth Bass sound which were not velocity sensitive instruments, period. Check the Voice program. Either way, in the MX the Arp phrase will be played at the originally programmed velocity.

It should come as a surprise to no one that as you move up in price in any product listing, the more elegant and often the more programmable the instrument becomes.

Thanks for the detailed answer!
This gives me a lot of thoughts that would be good to talk about in detail, but halfway with language barriers it can’t be overcome even with the google translator so much that we can completely take over each other’s philosophies from different cultures, e.g. I am from Eastern Europe.

Well, I would make an experiment ...
In my country, earnings are not nearly at the level of most people who lives e.g. in USA, where people can easily do so to buy a new car from their 1-2 month earnings or replace their instruments with a newer one every 2-3 years. My lot of friends are starting to immerse in the possibilities only these days, that were the trend 15-16 years ago, e.g. by purchasing a used Motif ES now... Namely, the price of such a flagship synth falls to 1/3 - 1/4 part in 10-12 years on the used market, which is financially available to most people.
Manufacturers are profit-oriented this can be stated. These days, I’ve just been talking to one of my musician friends that a giga company like Yamaha might not be aware of the possibilities for buyers in small countries. Now, a bit of a contradiction to it that this point is mentioned at MX here, which is a cheap model. Perhaps, this could really be communicated to the manufacturer in the following way: people don’t think about that cost cutting is main possibility by software simplification, but rather in terms of the quality of used materials or simpler keyboard design, quality of keys, display size... This is explained by the fact that same features is not necessarily a much higher development cost after an advanced synth. Simplification from certain level or optimization after simplification or new smaller software, planning from base that's maybe occour more development cost.

Many times people are unclear on the similarities and differences in the products.

Which shows incomplete knowledge of the functions can be found in the poor communication of the manufacturer. Marketing magic sentences often obscure reality. For example, I am also personally opposed to the advertising industry’s over-influential buyer tricks. For the simple honest man, the truth of the spoken word only matters de facto, it is the basic philosophy, not the slogan of well-music advertising. Unfortunately, I don’t think this can get in the ears of a Yamaha-level company management either. 🙂
I’m glad I was able to describe these here for now.

No, not at all. Velocity Mode is fixed to play the originally programmed velocity for the Arp Phrase (as it was originally created).

Finally, the specific issue is addressed in MX, where there is a bass program that senses dynamics with arpeggio. Name: 035 Big Cabinet
I don't know, can this setting parameter be found in VycoPro? (I'm not near my MX yet.)

Finally, the specific issue is addressed in MX, where there is a bass program that senses dynamics with arpeggio. Name: 035 Big Cabinet
I don't know, can this setting parameter be found in VycoPro? (I'm not near my MX yet.)

I don’t know about VycroPro, but you can certain reach Velocity Mode in the John Melas MX Editor.
Link: John Melas MX Tools

I could respond at length but your view of things is your view — I’ll just say you couldn’t be more wrong.

in USA, where people can easily do so to buy a new car from their 1-2 month earnings or replace their instruments with a newer one every 2-3 years.

Really!?! Is that what you think?

My friend's brother-in-law lives in USA and I know financial things from him.
One fact: There are many people in Hungary who live on $ 230-330. A new car costs 40-50 times more. (e.g. Kia Ceed) A Montage costs more than $ 3200.

Vycro software on USA Yamaha site

OK! This dynamic arp feature is available in the free Vycro Pro editor also.

@djuice

The Vycro Pro link you left doesn't work for me. I'm guessing that since the official development of Vycro Pro has folded (site down for some time) - the Faq was removed.

This is what is in cache:

Last Update: 9/24/2015

MX49, MX61: Use Vycro MX Editor to Create Multiple Splits or Layers in a Single Performance

NOTE: MIDI receive channel and note limit settings are not available from the MX instrument panel. To edit these parameters the Vycro MX editor must be downloaded here and installed and the Yamaha Steinberg driver must be downloaded here and installed for MIDI communication with the software. To use the performance after setting it up the [PART SELECT] button must be pressed.

1) Open the Vycro MX Editor.

2) Press the [PART SELECT] button on the MX keyboard.

3) In the Vycro MX Editor MIDI page, set the parts to the desired MIDI channels.

NOTE: the MIDI channels correspond to the [PART SELECT] buttons on the MX keyboard. In the following image parts 1 and 2 will both be triggered by the keyboard after the Part Select [1] button is pressed on the MX, parts 3 and 4 will both be triggered after the Part Select [2] button is pressed, parts 5 and 6 will be triggered after the Part Select [3] is pressed, etc.

4) If a split is desired, set the low and high note limit settings on the NOTE RANGE page.

NOTE: In the following image parts 1 and 2 will both be triggered when the Part Select [1] button is pressed, but part one will only be triggered by notes C3 and above and part 2 by notes B2 and below.

NOTE: in some cases, a voice’s arp will continue to trigger the voice even if the note limit is set. To fix this issue set the part’s Arp Note Limit to match the voice on the ARP 2 page.

The Vycro Pro link you left doesn't work for me. I'm guessing that since the official development of Vycro Pro has folded (site down for some time) - the Faq was removed.

Jason, where saw you the shared link? I also shared the Vycro Pro free version link on Motifator.com / MX forum, but here is again if it's required for you (or anyone). It's legal fully. — https://www2.zippyshare.com/d/DxRBwwFT/896/Vycro_MX_Pro.zip

https://usa.yamaha.com/support/faq/?c=&k=vycro

I was commenting about your message:

My friend's brother-in-law lives in USA and I know financial things from him.
One fact: There are many people in Hungary who live on $ 230-330. A new car costs 40-50 times more. (e.g. Kia Ceed) A Montage costs more than $ 3200.

Vycro software on USA Yamaha site <--- THIS

You had left a link (bolded above). The link address is: https://usa.yamaha.com/support/faq/music_production/8919.html

... and, for me, it didn't show any FAQ. However, I pulled the information out of a search engine's cache and posted it here.

(By the way, things from Yamaha are as cautious as this forum, registering again and again when you log in ...)
???

I pulled the information out of a search engine's cache and posted it here.

All right, I see also and thanks for your notice.

Missing information? This is the Yamaha Corporation. :p
(I have a musician friend and Yamaha asked him for endorser many years ago to the Tyros 4 line presentation. He didn't receive any response and help in support of his work unfortunately!)