Hi Hugh:

You need to get a latching foot switch. The FS assign is globally set in Utility/MIDI I/O, "FS Assign" and what you want to do is a Performance level setting. In order to do what you want an actual latching foot switch is needed.

I'm in the same boat as Hugh. I just bought a Montage M7 and would like to be able to control (and latch) rotary speaker speed not only by footswitch, but also by using aftertouch for when both hands and both feet are busy. I am able to do this on my Kronos, and I remember being able to do it on my old Motif ES8 and Rack ES.

Like Hugh, I would like to be able to use the footswitch for other purposes in other performances with the ability to configure the mode as either momentary or latching. The feature should not be difficult to implement. Can we put it on a wish list for a future FW update?

Curious - your reply to an 8 yr old thread shows up! I just mention that so you won't wonder why if you can't see any replies after your one in this thread. The forum appears to be broken and isn't showing replies when people post new threads. So there may be something about an old thread that avoids the problem.

I would like to be able to use the footswitch for other purposes in other performances with the ability to configure the mode as either momentary or latching. The feature should not be difficult to implement. Can we put it on a wish list for a future FW update?

You can post 'wish list' things on Yamaha's IdeaScale site: https://yamahasynth.ideascale.com/c/

The Yamaha dev team reviews IdeaScale weekly looking for suggestions for improvements and new things.

 I just bought a Montage M7 and would like to be able to control (and latch) rotary speaker speed not only by footswitch, but also by using aftertouch for when both hands and both feet are busy

I can't tell if you have something specific you need help with or if you are just wanting some additional functionality so bear with me if I get it wrong.

The ribbon can provide 'latching' of the new rotary speaker effect by setting up 3 ribbons: Off, Slow, Fast. See the 'First Four Drive' performance on the 'Edit -> Common -> Control -> Ribbon Settings screen. That performance is already set up to use the ribbon for slow/fast speed control.

All it takes is touching a finger in one of the three highlighted grid areas to change the speed. For me that is much easier than trying to use a footswitch. And I usually need the footswitches to control other things that really need footswitches rather than just latching.

The other issue I have is a footswitch usually kicks out a value from 0-127 and my foot isn't very good at changing smoothly from one end of the range to the other. 

You can use a knob or motion sequence to break a large parameter range (0-1023 now on the M models) down into smaller group values. 

Is there a specific problem you are trying to solve?

Meanwhile here is an old thread where Jason provides more info about the footswitch 'latch' topic.

https://yamahasynth.com/community/modx-series-synthesizers/how-do-i-setup-rotary-speed-control-on-the-modx-via-a-footswitch/#post-74576

use search box above for 'footswitch latch'