For me, montage_en_rm_a0.pdf ( https://usa.yamaha.com/files/download/other_assets/9/812529/montage_en_rm_a0.pdf ) page 155 doesn't have that. It's on page 141. It doesn't change your question - just in case others are looking for the doc reference.

Q2: The Edit-Operator-Form/Freq allows each individual operator (carrier or modulator) to have a unique pitch envelope. You'd want this for a variety of reasons. Maybe you only want to change the timbre of the sound over time using an envelope. Using the operator-level Form/Freq envelope - you can accomplish this without changing the actual pitch of the carriers (final output). Or maybe you want to affect the pitch over time of some carriers and not others. Or maybe just the carriers but not change the timbre and avoid changing the pitch of modulators.

The Part common level PEG is "the same" PEG found in the DX7. The way it works is that the PEG envelope is applied to all operators simultaneously (and identically). Since FM-X has some lineage to the DX7 and tries, at some level, to maintain some compatibility with the DX7's operation - you can look at DX7 documentation to help fill in some gaps where perhaps FM-X doesn't spell out what's going on.

Something like: https://www.deepsonic.ch/deep/docs_manuals/yamaha_dx7_basic_fm_synthesis.pdf or more official documentation.

Q3: For me the documentation on Montage A0 reference is page 145 ("butterfly diagram" and break point).

This is about level scaling as you play notes to the right and left of the break-point MIDI note. Linear scaling will higher and lower levels at a constant rate with every next key as you travel up (or down) from the break point. With exponential, you will have smaller level changes near the breakpoint and greater level changes the further away you get from the breakpoint.

https://yamahasynth.com/learn/synth%20-programming/fm-101-part-five-expanding-your-sound

Above outlines/defines what it does and gives some experiments to try to train yourself how it works in practice.

This is about level scaling as you play notes to the right and left of the break-point MIDI note. Linear scaling will higher and lower levels at a constant rate with every next key as you travel up (or down) from the break point. With exponential, you will have smaller level changes near the breakpoint and greater level changes the further away you get from the breakpoint.

https://yamahasynth.com/learn/synth%20-programming/fm-101-part-five-expanding-your-sound

Above outlines/defines what it does and gives some experiments to try to train yourself how it works in practice.

Thanks.

Wow. Just read through those FM 101 tutorials. There's no way I would have understood all that from just the Diagram or MODX/MONTAGE manuals.

Going to have a look through the "Manny's FM-Xploration" tutorials now recommended by BM.

Regards Q1.... is this a typo regarding velocity? Or is it correct, correlation to be discovered in deeper FM Guides?

Q1 I believe is a typo borrowed from the parameters (cut-paste error) that are velocity related. This one slipped past the editors / reviewers apparently.

Since FM-X, at the core, is basically the FS1R implementation without FS1R's formant shaping - the FS1R manual gives a better summary of what this parameter is all about.

Source: https://synthpalace.com/SynthPDFs/FS1R%20manual.PDF

10 (N:08): Resonance (V & N)
❑ Resonance
❑ Settings: 0 … 99
This parameter is only effective when the “res1” or “res2” spectral form (see “Form” parameter, above) is selected. It
determines at which harmonic a resonance peak is produced. Higher values produce a resonance peak at higher
harmonics of the fundamental pitch.

Thanks for clarifying. Keeps me sane. 😀