well i had a go at doing it, - once - and it seemed to be that you can run the sysex message inserting it at the top of a Song, and then once it's done, it's set and you can go mess around in pattern mode. but you'll have to run that song each time you switch the QY on. so i dunno, maybe use the last Song #20 as a utility song, with just that sysex message inserted at the top of the tracks/channels you want to mute; btw the message is preset so you don't have to compose it, just browse the list.
this is all a bit more arduous than on the RM1x, where it's its own setting on one of the system pages.
