Montage's operator output level ranges from 0-99, matching the DX7. Therefore, using the sine wave - the graph should match the DX7.

@J :
Thank you.

(I have ask the question because the DX21 (page 168 of the book) have also output level from 0 to 99 but different values for modulation index.
Not very important. Just for studies cases.)

Previous thread conversations (responses by Yamaha) indicate that FM-X is more closely tied to the DX7 family implementation than the DX21. Stated compatibility would seem to indicate that the lookup tables / internal workings are based on DX7. Given that (granted - an assumption - not a hard fact), I focused on the page 58 graph and offered the only item I could think that would alter the result - which is the span of level (since level span has sometimes been 127 instead of 99 in some implementations). Given the span is the same (99 max) - and if the assumption holds true - then the graph on pg. 58 should work. This is not adjusted, however, for the additional operators available on FM-X so you'll need to "draw within the lines" in using the graph.

It's a fair question - one I can't answer - if the assumption is true.

You can check, I suppose, by test/measurement. It would help to have a DX21 (or related) handy to make sure your test setup is valid as the DX21 (or related) would follow the trend of the graphs. And if this holds true - you can validate your general test approach then make the same measurements on Montage.

There may be a more rigorous approach. I haven't read through the theory to see if one can derive a formulaic method of arriving at the values. I have some "gut" notions of why these differences are there - but I'd rather yield to someone who may benefit more from doing the research -- or, better yet, to someone who's already arrived there and knows the answer without any time investment.

@ Jason:

I will consider that these index values are valid for Montage.
(I have no other way to check it anyway.)

And thank you for your answers.