envelope filter

An envelope filter is a filter effect that produces a watery, wah-like sound controlled by the strength of your playing rather than foot movement¹². It is based on the same circuit as a wah pedal, with a voltage-controlled filter circuit that reacts to the intensity of the incoming signal to determine the depth of the wah sound¹³. The pedal detects the level of your playing and moves the filter cutoff up or down, so harder picking produces a more pronounced effect³². It is often mislabeled as an auto-wah, though the two are differentiated by how their sounds are enabled¹. Notable users include Frank Zappa, Jerry Garcia, and Pete Townshend, and the effect has also been used on bass by Flea and Bootsy Collins⁴.