Nux Mg300 Multi Effect Guitar Pedal

The expression pedal can be used to control the volume or the effects. wah: controls the wah filter. efx: controls gain (drive) parameter of od/dist. or controls pitch parameter of pitch bender. amp: controls level parameter of amp. mod: controls mix level of modulation effects. dly: controls mix level of delay effects. rvb: controls mix level of reverb effects