Your question seems a little mixed using "voices" and referencing "256". Since "256" and relating what you are asking, I come up with a rephrase of your question:

What are the rules on Montage that determine the maximum polyphony for both AWM2 and FM-X synth engines?

Rather than rephrase an answer, there is a great discussion already "in the archives" which I dug up through a search-engine search.

https://www.yamahasynth.com/forum/intro-and-a-few-questions#reply-7001

Thanks for your reply Jason.

I had missed that post.

OK, every element takes one voice/polyphony.

Thx

Thomas wrote:

Thanks for your reply Jason.

I had missed that post.

OK, every element takes one voice/polyphony.

Thx

Only if it is sounding. If you don't add that bit, you will miscount the polyphony used. Only if it is sounding. An electric piano sound could be 6 Elements. Let's use the "Vintage'74" Performance as an example.

Element 1 only sounds when Velocity = 1-63
Element 2 only sounds when Velocity = 64-105
Element 3 only sounds when Velocity = 106-122
Element 4 only sounds when Velocity = 123-127
Element 5 only sounds when you release a key (XA CONTROL = Key Off)
Element 6 only sounds when A.SW2 is On

So this six Element Part uses only one note of polyphony when any single key is struck, but if the Assign Switch 2 is engaged it uses two notes of polyphony per key played.

So you can see your conclusion is far from correct.

You can see this by playing the "Vintage'74" Performance while in Part 1 Edit... The bottom of the screen will show you the active Elements and their activity as you play. See screenshot below.

Thanks for your reply Bad Mister

Yes i like the XA part in the AWM engine.
Very useful and powerfull.
I use it a lot.

I correct myself, I should have said.

"Every element takes one voice/polyphony when sounding."