You are correct. You cannot set one H9 footswitch to scroll up and the other to scroll down.
Also, you need at least one aux switch and/or an expression pedal to accomplish what I describe. I too place a premium on simplicity, but there is so much jammed into the H9 I can’t complain if I have to add an aux switch or an expression pedal. Options explode when you do this … including solving the volume pedal issue you have.
Let’s start simple and say you add one $30 aux switch and link it to the hotswitch function of any Space or H9 algo. The key to avoiding any lag is to stay within one preset. In this example, I’ll use the Spacetime algo.
For a verse, set up a preset with a simple slapback delay. Then, program the hotswitch for reverb, but no delay, for a chorus. Calling up that preset in the future starts the slapback, but also allows you to instantly toggle between the two effects with the aux switch.
Too simple … tivial you say?
For a verse, set up a preset with a chorus going dual delays set with the Fibonacci sequence for stereo ping pong . Then, program the hotswitch for a Leslie with reverb on fast rotor (but no delay) for a chorus. Calling up that preset in the future starts with the Fibonacci delay, but also allows you to instantly toggle between the two effects with the aux switch.
Don’t like that? Let’s try some others … pick any one of the Spacetime factory presets for a verse. Then program the hotswitch to match any of the other Spacetime factory presets for a chorus. Now toggle between the two to your heart’s content. Want to see how diverse that is? Change your control app to the “PEDAL VIEW” and watch the signal routing configurations change as you step through the various factory presets. IMHO that’s pretty amazing and all we’ve added so far is one simple aux switch that costs about $30.
Are you willing to spend $100? Then get a Disaster Area MIDI BABY (with one footswitch) and you can execute three different functions with one tiny little box. You could add a clean boost capability to anything mentioned above. And, you could add that scroll down function you wanted too.
Now add an expression pedal and you can add a third effect choice (still within that one preset): verse = basic sound = heel down … chorus = different sound = toe down … bridge = hotswitch.
Want to forever solve that volume pedal problem that vexes you? Plug that expression pedal into the expression pedal 1/4″ jack on the MIDI BABY and link it to the output fader (or the input fader – your choice) control change midi parameter. Done.
There is no lag or glitch with any of this and we haven’t even left the SpaceTime algo yet. There are 21 other algos that also have the hotswitch. You can explore those too.
No let’s say you want your favorite Spacetime preset for a verse and to switch to your favorite Tricerachorus preset for a chorus with no lag. Can we do it? No. Not with one H9. Sorry the options are many but they are not infinite.