Here are some instructions I had written some time ago to help someone else, and which you can use. At that time, the request was the opposite (wah to the left pedal, and global volume to the right pedal). It's easy enough for you to flip these around to suit your needs.
First, the wah block. I'll guide you through the process of changing it so that the wah is controlled by your X15 expression pedal on the left.
Before I get into the step-by-step, a quick explanation. In a block, many parameters can be assigned a modifier. A modifier is something that will affect the value of the parameter. The modifier can be an LFO (like an autowah), an envelope (how hard you hit the strings will set the value of the parameter), a sequencer (you program the various steps of the sequencer and it will shift through all of those values), or one of eight "external" controllers. In our example, we will assign your left expression pedal to external controller 1, and then we'll assign external 1 as the source for the modifier assigned to the "freq" (frequency) parameter of the wah block. Don't get overwhelmed by the above, it will all make sense eventually.
So first step: let's assign your left expression pedal to "external 1". On the front panel of the Axe-FX,
- Press the "I/O" button
- Press the "PAGE >" button three times to go to the "CTRL" tab
- Scroll down to the "EXTERNAL 1" parameter (it should say "NONE")
- Now, hit the "ENTER" key - this places it in "learning" mode, which automatically detects your expression pedals and continuous controller.
- While in "learning" mode, activate your left expression pedal back and forth... the value for "EXTERNAL 1" should now change to reflect the CC number of your left expression pedal. On mine, the left expression pedal is #127 (yours may be different, depending on what was done at the X-15 end).
- Now that "EXTERNAL 1" is set to the value of your left pedal, you can hit the "LAYOUT" button to go back to editing your preset
Second step: let's assign External 1 to be the modifier for the wah's frequency:
- Select the preset you wish to edit
- In the layout menu, place your cursor on the wah block, and hit the "EDIT" button
- On the "BASIC" tab, press ">" (the navigating button) 5 times to place the cursor on the "FREQ" parameter
- Hit the "ENTER" key to go into the "MODIFIER" menu (note: any parameter that has [ ] below it or next to it can be assigned a modifier to change the value of that parameter).
- Change the value of the first parameter there, "SOURCE", from "NONE" to "EXTRN 1"
... you can immediately see the results: while still in the MODIFIER menu, activate your left expression pedal back and forth, and you will see the dot move up and down on the diagonal line on the graph; if you have sound going on, you'll also hear that your wah is now controlled by your left pedal.
- Hit "EXIT" to leave the modifier menu. You're done.
Note: this will probably be a pretty bad wah. You'll want to tweak several of its parameters, and you may also want to change how it responds to your left pedal. You can change the curve from the modifier menu by changing the "START", "MID", and "END" values. You can also shape the resulting curve by adjusting the "SLOPE", "SCALE" and "OFFSET". I'll leave all of that to you. You can look at downloaded presets to see how others have tweaked their wah blocks, it will be a great learning opportunity. But for now, you should be able to do the simple modifier assignment I described and get at least rudimentary control of your wah using your left pedal.
Now, for the volume... here, I will show you how to assign your right pedal to the global OUTPUT 1 level. Contrary to my first example with the wah block, here we'll be assigning a CC to a global parameter. As an alternative, you could add a volume block in the preset's signal chain, and assign you right pedal to EXTERNAL 2, for example, and then set a modifier on the Volume block's "VOL" parameter set to EXTRN 2. This would then work just like above. The nice thing with this is that you can place that volume block wherever you want, I like to place it after the amp and cab block, but before the reverb and delay, because that lets your reverb and delay tails ring out when you lower the volume. Using the above description for the wah block, you should be able to do this. But here, I'll describe how to assign your right pedal as a global CC assigned to Output 1 volume level. This will obviously *not* let the reverb and delay trails ring out.
Only one step needed to do that:
- Press the "I/O" button
- Press the "PAGE >" button three times to go to the "CTRL" tab
- Scroll down to the OUT 1 VOLUME" parameter (it should say "NONE")
- Now, hit the "ENTER" key - this places it in "learning" mode, which automatically detects your expression pedals and continuous controller.
- While in "learning" mode, activate your right expression pedal back and forth... the value for "OUT 1 VOLUME" should now change to reflect the CC number of your left expression pedal. On mine, the right expression pedal is #1 (yours may be different, depending on what was done at the X-15 end).
- Now that "OUT 1 VOLUME" is set to the value of your right pedal, you can hit the "RECALL" button to go back to regular preset recall mode.
Test it all out, now your left pedal is assigned to the wah (in the edited preset *only*), and your right pedal is assigned to the Output 1 volume level (for all presets, as this is a global setting). You understand the difference? Again, the alternative is that you can follow the "wah" instructions above to assign instead your other pedal as an external controller again, and edit your preset to assign that external controller to a modifier on the Volume parameter of a Volume block.
Play around with all this, and let me know. I'm hoping that my step-by-step instructions were clear enough. Any questions of glitches, don't hesitate to contact me.
All the best,
Daniel