A wah pedal uses a filter to sweep through a wide frequency spectrum, boosting and exaggerating specific tones. As the sweep approaches the higher frequencies, the result is vowel-like sounds reminiscent of the human voice. In the earliest wah pedals, this sweep was controlled by manual manipulation of a footswitch reminiscent of a see-saw. With the DW400, the sweep occurs automatically according to your control specifications. Or you can plug in an expression pedal (not included) to go old-school. And with BERHINGER’s Real Sound Modeling technology, the DW400 emulates the human voice like nothing of its kind.