I'm a little late to the party on this, and while MGX may not be referenced in the manual, I did find this in the Help:

The [Copy Melody to Melody Track] is a utility function that should only be used when the style is "finished." Prior to executing this command, the Melody track contains the entire MIDI file with all of the parts. This "MIDI-file-on-the-Melody-track" is used to create the style. Once the style is created, you might want to extract the actual Melody track from the MIDI file to put on the Melody track. The channels used are the channels that have the BB Part set to "Melody." When you do this command, you get a chance to first save the MGX file (i.e. the file with the MIDI file on the Melody track), so that you can revisit the file. This "Copy Melody to Melody Track" is useful to audition your new style, because you can then hear just the Melody along with your style.


BIAB & RB2024 Win.(Audiophile), Sonar Platinum, Cakewalk by Bandlab, Izotope Prod.Bundle, Roland RD-1000, Synthogy Ivory, Kontakt, Focusrite 18i20, KetronSD2, NS40M Monitors, Pioneer Active Monitors, AKG K271 Studio H'phones