No se si lo han visto, pero hay un editor gratuito para Montage/Modx/Modx+
http://miditracker.org/montage.html
Features
Part Mixer
quick-edit all 16 parts on one page
copy patch / part EQ / part FX settings from other performance part / variation
FM matrix editor with automatic algorithm selection
multi-edit, cycle, shuffle, randomize operators
Envelope mixer
morph between PEG / AEG / FEG preset envelopes
randomization
persistent EG mixer state (saved per part variation / FM operator / AWM2 element)
FM Sound mixer
morph between 4 FM-X patches
can (optionally) morph each operator separately
randomization
persistent sound mixer state (saved per part variation)
AWM2 element editor
reads user waveform names from text file (montage_user_waveforms.txt)
Part LFO editor
utility functions for generating / modifying user LFO waveform
Part Controller Box (mod matrix) editor
15 global banks * 128 patches / performances (A..O)
1 project-specific patch bank (P)
up to 16 parts per performance (AWM2, FM-X or DRUM)
part layer flag: automatically play neighbouring parts in editor
play layered parts from sequencer by sending notes to proxy node automation port A/B
rearrange parts via drag'n'drop
up to 16 variations per part
technically up to 16 performances per patch
utility functions to sync part Level / CtlBox / FX / part EQ / master EQ/FX from Main variation
variation changes can be sequenced via proxy_layer_[1..16]_prgchg RPN (proxy node automation port A / B)
select part variation via F-2+C-4..D#5 synth key combo
part variation changes can be recorded back into sequencer
either via synth key combos
or by selecting part variations in the editor UI
up to 32 variation scenes
change all part variations at once (or keep current part variation)
select variation scene via F#2+C-4..G-6 synth key combo
variation scene changes can be recorded back into sequencer
either via synth key combos
or by selecting variation scenes in the editor UI
option to force part outputs to "Main L&R" / "Asgn L&R"
option(s) to remap sliders (and change mapping via synth key combos)
part volume (F-2+B-3)
current part assignable knobs 1..8 (E-2+B-3)
part 1..8 assignable knob 1/2/../8 (E-2+C-3..G-3)
part 9..16 assignable knob 1/2/../8 (F-2+C-3..G-3)
En el foro de Yamaha hablan muy bien, no lo he probado... pero hay videos que muestran FM sound morphing / randomization & Variation scenes