You can control any pedal or Instrument that offers an Expression or CV Input. The effects Lewis has on the connected Pedal or Instrument will be widely different, depending on the type of pedal/instrument and on which parameter you'll be controlling. Depending on the polarity of your connected Effect Pedal or Instrument, you may need to use Lewis' onboard switch to adapt the polarity.
To simplify things (and because it's fun), we call all compatible devices 'Clark'. Our favorite Clarks are: any Moog MF pedal, any pedal by Meris, the Pyramid by Earthquaker Devices, Tremotron by Stone Deaf and the awesome Prophet 6. It is important to know, that we cannot guarantee compatibility with every single pedal or instrument available, because some devices use a custom signal type to be externally controllable (e.g. Stone Deaf's PDF-2). If you're unsure, contact us.
How you bring in Lewis into your live set is your choice all alone. Lewis' expression pedal input gives you an additional option in how you you use it in a set or a single song. For instance: by connecting your expression foot pedal to the depth parameter, you're able to fade in or out Lewis' effect on your chosen Clark (the stompbox connected to Lewis) whenever you want to. Lewis' strength of course is laying down a solid rhythm to build upon. You can turn your filter pedal into a Tremolo/Vibe for the verse, and deactivate it for the chorus to make it sound fuller automatically.
→ Check, if your Lewis is properly connected to a suitable power source.
→ Check, if your Lewis is engaged (big LED is glowing). If not, press the On/Off Switch to do so.
→ Check, if the polarity of your connected effects pedal or instrument is matched on your Lewis (onboard switch).
You can use any expression pedal that either offers TRS or TSR polarity. Make sure, that the needed polarity is matched by your Lewis. Adjust the onboard polarity switch if necessary.