The way I have always figured out that levels work, is that MIR needs an even level input to it, so that the Natutral Volume can then do it's thing.  The volume in VI Pro seems to be set, so that a maximum level of about -10 is always sent to MIR.

When I set up my own Presets,  I set the VI Pro volume so that the maximum output level is about -10 (with the mixer level at 0), then let MIR take over control of the level.  This is only a starting point, and further adjustments will need to be made, but I think this explains why various Presets have different volume levels.

Perhaps someone from VSL can confirm or deny this, as this is only what I have discovered, and the way that I start out with things.

"Natural Volume' is [...] a suggested starting point"

@BachRules said:

Natural Volume [...] a real, objective measurement, not a matter of art or taste.

VSL has the answer. They know exactly how the VI Pro volume should be set in order for the MIR "Naural Volume" to work as designed. It's just a matter of their withholding that information from their customers.

I don't know where 'a real, objective measurement' comes from. I guess if someone only ever uses VSL Samples and MIR Pro it comes off as a more or less naturalistic out-of-the-box experience, but I've seen this asked several times here and that's my received answer. First time I noticed it, it was 'I'm not hearing enough of this instrument' and I adjusted for it. And that isn't I think very unique to me.

Dietz wrote [in the thread MIRx Clarinet natural volume]: "In any case - if the Natural Volume setting for the Clarinet is not to your liking, just reduce its volume by two or three dB. If the instruments seems to be too dry and up-front, bring up the wet signal a bit. After all, Natural Volume is meant to be used as a convenient starting point for your own creations. It can't and won't replace an individual mix for every new arrangement."

@Another User said:

"Natural Volume' is [...] a suggested starting point"

I'm basically parroting there what I've seen someone from VSL, perhaps Dietz, state about the matter on this forum.

Dietz is in the habit of telling people there are no rules, and whatever sounds good is good. When it comes to Natural Volume, however, there are rules, and those rules are called The Laws of Physics. You cannot see people fly in the real, natural world, because The Laws of Physics. You can see them fly in the movies, and that's like when you use your DAW to deviate from Natural Volume. Sometimes you want people flying in your movies, but sometimes I don't. I just want it to sound authentic, and that's hardly a revolutionary idea. With Mural, you just load the patches and play, and you get Natural Volume, because the players were recorded in place, and the samples were never normalized. VSL was recorded differently, but there's nothing to stop us from getting Natural Volume out of VSL, if only VSL were willing to give us the information we needed to do that. Mural doesn't make you jump through hoops to achieve Natural Volume.

From another thread:

"The two (or actually three) things to keep in mind are:

1. Natural Volume makes only sense when it gets used for all instruments of an arrangement.

2. Due to the huge dynamic range covered by the different instruments of an orchestra, most instruments bar a very few have to be set to surprisingly low volumes, to allow for the necessary headroom of the few loud ones. If your arrengement seems to be too quiet then, either raise the volume*) of all instruments by the same amount, or simply bring up your master bus' volume to meaningful levels.

3. Natural Volume is meant to be used as a starting point. Don't expect this feature to be the answer to all your mixing tasks.

*) "Raising the volume" is not the same as "using a louder dynamic layer"!

BTW - this is what MIRx' Manual tells us about Natural Volume on p.11:

@civilization 3 said:

Dietz wrote [in the thread MIRx Clarinet natural volume]: "In any case - if the Natural Volume setting for the Clarinet is not to your liking, just reduce its volume by two or three dB. If the instruments seems to be too dry and up-front, bring up the wet signal a bit. After all, Natural Volume is meant to be used as a convenient starting point for your own creations. It can't and won't replace an individual mix for every new arrangement."

Thanks for quoting that. I take his advice there to mean, "If you want to make it less natural, go right ahead and change the levels away from Natural Volume." But, that doesn't apply to me, as I don't want to make it unnatural. I want Natural Volume, which is a major factor why I bought MIR.

@Another User said:

"Natural Volume' is [...] a suggested starting point"

I'm basically parroting there what I've seen someone from VSL, perhaps Dietz, state about the matter on this forum.

Dietz is in the habit of telling people there are no rules, and whatever sounds good is good. When it comes to Natural Volume, however, there are rules, and those rules are called The Laws of Physics. You cannot see people fly in the real, natural world, because The Laws of Physics.

You're on your own, you know better than I do apparently. I'm not going to take time to sort you out if you're going to insult my intelligence.

@civilization 3 said:

From another thread:...

But unfortately that sheds no light on the issue of this thread: How to set VI Pro Volume (CC7) so that it doesn't work against MIR's Natural Volume adjustments.

Any wrong CC7 setting will defeat the purpose of MIR's Natural Volume adjustments. In order to avoid wrong CC7 settings, we'd need to know which CC7 settings are right. For that, we'd need VSL's cooperation, and that's what's missing here.

@Another User said:

I'm not going to take time to sort you out if you're going to insult my intelligence.

Bye.

@civilization 3 said:

The volume of amplification does not impact timbre, though, for starters.

As if I claimed it did?

* In fact there are in every recording studio. LOL! Where in your experience does this dogma derive from?
[Rhetorical Question]

@Another User said:

In fact there are in every recording studio. LOL! Where in your experience does this dogma derive from?

Does your experience in recording studios entitle you to tell me which chords and notes to compose too, or only how I should adjust my volumes in my own compositions?

The "dogma" you're railing against is all in your head. I'm just asking how to operate this computer program in order to get it to function as advertised. Your music isn't important enough to me for me to care how you set your own levels; please understand that. You took my request for customer support, and you made it about your own music, in your mind. It's not really about you and your music. I've never given a moment's thought to your music; understand now?

I'm not interested in you, as your point seems only to take offense from my request for customer-support on a company's customer-support website.

Come on guys, no need to bicker. The question as I understood it is simply: how do the volume faders in VI Pro have to be set to use the natural volume feature of MIR correctly. Indeed a clarification from VSL would be welcome, and I'm sure they will give an answer once they get aware of the question. Their support is really great and they are as helpful as you could wish. So, I'd simply write an email to their support aksing the question.

Meanwhile, the logical solution would be to set the volume sliders in VI Pro to the same value for each instrument. Maybe try this and listen if it gives you meaningful volume correlations? If something is way off that way you should be able to easily hear it. Otherwise you have a working solution until VSL answers your question.

By the way, the Dynamic Range slider in VI Pro will have an influence too. I guess this one too should be set to the same value for all instruments when working with 'Natural Volume'.

@Another User said:

I guess this one too should be set to the same value for all instruments when working with 'Natural Volume'.

I'll refrain from speculating, and wait for VSL to clarify. It also raises the question which Dynamic-Range setting gives the natural amount of dynamic compression/expansion, and which ranges result in unnatural amounts of dynamic compression or expansion. (OT provides this info about BST in their manual, and I for one appreciate it greatly.)

Thanks for your constructive input on this.

Let me interject as well. I will agree with BachRules that achieving a natural sound is really science, and my motivation in buying MIR Pro is that I wouldn't have to worry as much about volumes, EQing, and mixing in general. After I downloaded a demo version of MIR Pro, I realized that I actually do have to worry about these things. For example, in regards to natural volume, I was doing a piece with a timpanis, and strings, and I set everything to "Natural Volume", but the natural volume of the timpani sounded way too load to even be considered natural to my ears (my VIPRO volume was set to 127 for all). I'm talking loud! I had the same experience with the Epic Horns (8 horns). Too loud to be considered natural to my ears. If the Timpani is usually placed in the back, shouldn't the natural volume be lower? In both cases I was forced to lower the volume.

Anyway, I ended up buying MIR Pro because I think it does a great job that is close enough to natural. Maybe this feature will be refined in future versions. For now, I see it as a guide really.

@nektarios said:

///

 For example, in regards to natural volume, I was doing a piece with a timpanis, and strings, and I set everything to "Natural Volume", but the natural volume of the timpani sounded way too load to even be considered natural to my ears ///

A single Timpani player is quite capable of being heard over 40 string players, a forte Timpani is loud.

The solution is not to turn the Timpani down in volume,  but to play with softer dynamics,  

A forte struck Timpani at a reduced volume level is not going to sound right.

Just tell the Timpani player not to hit the Timps so hard !

I looked at the natural volume fader for the timpani and it is the highest compared to the other instruments. This seems wrong considering that a Timpani is really in the back. I tend to prefer softer dynamics for all instruments and the timpani simply sounded too load to be considered natural. I will send an example later.

Have you ever looked at the last page of the MIRx Manual? All values used for Natural Volume are listed there. Timpanis, Gongs, Piatti, Tamtams, Bass- and Snaredrums are the instruments with the smallest volume-offsets (read: By comparison they are the loudest ones.) 

HTH,